Ultimate Computer Troubleshooting Guide And Diagnostics

Your computer is dead. It will not boot. It was working the night before, but now when you hit the power button nothing comes up on the screen. But is your computer really dead? Or is it giving off subtle clues as to why it is no longer functioning normally? Our extensive computer troubleshooting guide will assist you in diagnosing and fixing most PC problems.

There are countless reasons why a computer will not boot. Typical symptoms for a computer that will not start are a blank screen, a blue screen, a never ending loop of restarting or a PC that is completely dead. Now there are also several reasons for each of those symptoms. Troubleshooting a computer that will not boot up can be a slow process, but if you tackle each of those symptoms, you can quickly rule them out and get to the real problem faster than you think.

Computer Troubleshooting Steps To Fix Common Issues

For starters, if the computer is still under warranty, do not open the case, as this will void your warranty.

HP, Dell and any other major manufacturer will respond quickly to your problems and arrange for you to send the computer in, or they might opt to send a technician out to work on the computer. If you bought the PC at a shop around the corner, send emails and begin a paper trail on the issue.

With that said, a completely dead computer will usually have either a bad motherboard, bad power supply, or a faulty case. The following computer troubleshooting steps will help you find which device is causing the problem. Well start with the easiest and work our way down to the hardest. One of the first things you’ll want to do is unplug the computer and take it to a table where you can lay it flat. Open the case and check the connections to see if you notice anything blatantly wrong, then proceed with the steps below.

Troubleshooting A Computer Power Supply

Power supplies can fail without warning. The worse part is, they can partially fail. This means you might be getting power to the motherboard, the fans and other components, but you do not have the correct voltages to start the motherboard.The power supply is located at the back of the case, and is where the power cable plugs into the PC.

  1. Your first step should be to plug the computer directly into the wall and bypass any power strips. You should also confirm the outlet is working properly.
  2. Make sure the red voltage regulator switch on the back is set to 115 if you reside in the United States, people in some countries will need to set theirs to 230. With the power off and unplugged, try toggling the switch to 230, then back to 115 to make sure it is seated in the right position.
  3. Next, buy a power supply tester. Computer techs will use a multi-meter to test for proper voltages. Normal users can just buy a power supply tester. These are cheap and easy to use.
  4. If your power supply is bad, buy one of equal or greater power. If your current power supply is 350 WT, be sure to get one that’s 350WT or higher. Shop for a power supplyTroubleshooting A Computer.
  5. If you have an HP computer, read these HP power Supply troubleshooting tips.

Troubleshooting A Computer

A power supply will tend to fail before anything else, as they take the most abuse. They are the front line when a power surge or brown out occurs. The good news is, they are extremely easy to replace should you find this is the problem.

Troubleshooting A Computer Case

While a dead PC will either normally be a bad power supply or bad motherboard, the next easiest thing to troubleshoot is the case. How can a case go bad? A case has minimal smarts, but it does have wires leading from the power button to the motherboard that can go bad, and some even have advanced I/O panels that can fail.

  1. You can try bypassing the case switch. This means you are initiating the power-on sequence without using the button on the front of the case. For this, you will need a good set of eyes and a small, flat-head screw driver. The idea is to find the wire leading from the power button to the motherboard that’s marked something like POWER SW or POWER ON. It will cover two pins on the motherboard. Carefully, with the computer plugged in, touch tip of the flat head screwdriver to both of those pins at the same time, thus “shorting” them. You will not get shocked by doing this, but you need to be careful not to scratch the motherboard. Read more on bypassing the case switch here.
  2. If you have a Dell computer, read how to test a Dell I/O panel here.

Troubleshooting A Computer Motherboard

The motherboard is the hardest thing to diagnose and replace. If your motherboard is proven to be bad, it must be removed from the case and replaced. Unfortunately, there’s a lot of stuff plugged into the motherboard, such as the CPU, RAM, PCI cards, Video Cards, hard drives, CD / DVD drives, power supply and fans. There are also tricky connections that must be made to the case’s power and reset switches. So replacing a bad motherboard is a long process. A bad motherboard will be determined by the following:

  1. If all of the above are not the problem, the motherboard is the problem by default.
  2. A bad motherboard might have visual signs of damage, such as bulging or leaking capacitors. See below.
  3. With the computer unplugged, try holding in on the power button for twenty seconds. This will drain the capacitors of any excess power. The computer might start up and work fine forever. If the computer starts, then fails again after doing this, then the motherboard is bad.
  4. Try removing any non-essential cards and drives in the computer. You do not need modems, sound cards, hard drives, CD / DVD drives, or floppy drives connected to boot. Our goal is to get a clean power-up situation, not boot into windows. If you remove non-essential parts and you still have no power, then the motherboard is bad.

computer will not boot

My Computer Has A Blank Screen

If your computer starts up, makes hard drive churning sounds, has lights on the panel flash but only displays a blank screen, you could several problems. You need to first confirm that the monitor is powering on and has the cables securely connected to the PC. You might even test the monitor on another PC to rule that out. If the monitor is good, make sure your PC is getting that initial start-up screen where is checks the memory and displays BIOS information. If you do get that screen, try tapping F8 until you see a boot screen that gives you an option for Safe Mode. If you can get into Safe Mode, it could be a video driver issue.

If you cannot get to Safe Mode, we need to next rule of the hardware of the computer. We recommend downloading and burning a Linux Live CD. By booting to a Linux Live CD, this rules out problems with the memory, the video card, the motherboard and most other devices connected to the PC. If you’re able to do this, you likely have a problem with your hard drive or the Windows installation on that drive. Try reinstalling Windows.

My Computer Keeps Restarting

If your computer will not boot because it is stuck in a reboot loop, this probably means you either have bad RAM, a corrupt hard drive or some other problem within the Windows Operating System. If you want to check your RAM for errors, try memetest86. You can also try booting to Safe Mode by tapping F8 when you first boot the computer. If you can get into Safe Mode, try a chkdsk in Windows. Chkdsk is available in Windows 2000 and Windows XP. To run a chkdsk, go to My Computer and right-click the drive you want to scan, then select Properties. Under the Tools tab, you will see a section for Error Checking. Click Check Now. and make sure the automatically fix errors box is marked. If none of that works, backup any data you can and reinstall Windows.

Computer is Completely Dead

If your computer will not boot because it will not power up at all, you could have a problem with the power supply, the motherboard, the CPU or even the case switch. The first thing you should do is disconnect any external devices–like speakers, printers, scanners, etc. Next, if your PC is plugged into a power strip, try plugging directly into the wall, as power strips can fail. If it still won’t power on, you should test the power supply to make sure you are getting the necessary voltage to the motherboard. If the power supply is good, try bypassing the case switch. If you are still getting no power, examine the motherboard for obvious damage to the capacitors. If they appear to be bulging or leaking fluid, then the capacitors have blown.

Summary For Troubleshooting a computer that will not boot

  1. Check the monitor to make sure it’s working. Check its cable or test the monitor on another PC.
  2. Try a Linux Live CD to rule out most hardware problems.
  3. Test your RAM with memtest86.
  4. Boot to Safe Mode and try chkdsk.
  5. Test the power supply, the case switch and look for signs of damage on the motherboard.
  6. If all else fails, reinstall Windows.

Computer Beep Codes

computer troubleshooting can be the most difficult when a PC only beeps at you when you press the power button. Your computer’s BIOS will often produce an audible beep code to indicate why it is not working. If you have a custom build and are not receiving a beep code, make sure your motherboard has a speaker attached to it as not all cases come with a speaker you can plug directly onto the motherboard.

Note: This is not an external speaker you plug into the back of the computer, it is a speaker that plugs onto the motherboard itself.

If your computer is producing a beep code, the next thing to determine is what kind of BIOS is running on that computer. If your PC is not displaying anything at all on the monitor, you may need to resort looking directly on the motherboard for the BIOS chip.

award bios

A few common BIOS manufacturers are AMI BIOS, Award, and Phoenix, and here are their BIOS beep codes.

Computer Diagnostic Lights

Some major brand name computers such as Dell, Lenovo and HP can communicate via diagnostic lights on the case, power supply or on the power button itself. The best way to determine what your computer is trying to say through these diagnostic lights is to visit the website of the computer manufacturer and read its online manual. For example, the Dell Optiplex 9020 uses a front power button diagnostic light that flashes when there is a hardware problem.

Dell power button amber light flash codes:

2 pause 1 – This indicates a system board failure

2 pause 2 – This could be a bad system board, PSU or PSU cabling problem.

2 pause 3 – Possible system board, memory or CPU failure

2 pause 4 – CMOS battery failure

2 pause 5 – The computer has a corrupt BIOS

2 pause 6 – CPU configuration failure or CPU failure

2 pause 7 – Your memory modules are detected, but there is a memory failure

If your Dell model has diagnostic lights on the rear of the computer, refer to this article on Dell diagnostic lights to determine the problem. If you have a different make computer, go to the manufacturer’s website support section and search for the manual for your computer manual.

Onboard UEFI Diagnostic Test

Your computer may have a Unified Extensible Firmware Interface (UEFI)–an advanced BIOS replacement–capable of running diagnostics. If you have a Dell, HP or Lenovo computer, for instance, restart the computer and begin tapping the F12 (for Dell), F2 (for HP) or F10 (for Lenovo) keys to launch the diagnostics. These diagnostics can tell you if there is a problem with your computer hardware. Below is a screenshot of a Dell diagnostic page:

dell diagnostic

If your major brand name computer does not have this functionality, you can create a bootable disk to run these diagnostics.

Download Lenovo diagnostics here.

Download the Dell diagnostic disk here. Type in your service tag (serial number) and then select the diagnostics drop down to download the disk.

Download the HP Diagnostic disk here.

Your Computer Is Slow Because You Do Not Perform Maintenance

Weekly Computer Maintenance

Your PC is not unlike a car that requires routine maintenance. Computers actually require a weekly, monthly and annual computer maintenance schedule. Computer maintenance should be performed at certain time intervals, and if that maintenance schedule is ignored, your computer speed will suffer and you could ultimately experience a computer system failure. Getting on a computer maintenance schedule or setting your PC to automatically perform weekly computer maintenance can help keep your computer optimized and running good for years to come.

Weekly Computer Maintenance Schedule

Note: It’s not feasible to ask the average computer user to manually keep up on weekly computer maintenance. So it would benefit you to setup a schedule so Windows performs these chores automatically.

Backup Files – You should start by making a backup of your data. We recommend backing up to an external hard drive. Here’s an easy way to schedule backups using Xcopy and task scheduler.

Or in Windows 7, go to the Control Panel>System and Security>Backup and Restore to enable and configure a backup schedule. You should backup to an external hard drive such as the Western Digital WD Elements 1 TB USB 2.0 Desktop External Hard Drive.

Disk Cleanup – Go to Start, Programs>Accessories>System Tools and select Disk Cleanup. Windows will look at your Temporary Internet Files, Recycle Bin and other files that are safe to delete from your computer. To schedule a Disk Cleanup, Click Start, Programs>Accessories>System Tools>Task Scheduler. Click Action, then Create Basic Task. Type in a name and click Next. Select weekly for and set a time for the Disk Cleanup to run and then click Next. Click Start a Program and then click Next. Click Browse and then type in cleanmgr.exe in the File Name box and click Open>Next, then Finish.

Full Virus Scan – While we recommend a virus scanner that updates daily and provides real-time protection, you should also run a full scan once a week. Check in your antivirus preferences for instructions on how to setup a weekly full scan.

For this weekly computer maintenance schedule to work, leave your computer on 24/7. Most computers can be configured to go into a low-power mode and wake up in the middle of the night to perform these tasks while you are not using the computer.

Monthly Computer Maintenance Schedule

Disk Defragmenter – Disk Defragmenter re-organizes data strewn about your hard drive so your computer can access files faster. You can also schedule disk defragmenter to run weekly at a specific time. Note: Newer generation PCs have solid state hard drives that should not be defragmented.

Clean Computer – Depending on the location of your computer, you should vacuum the area around your desk and inspect the internal and external fans to make sure they are free of hair, dust, and other debris that can cause heat-buildup in your PC.

Software Update – Most software will automatically tell you when an update is ready to be downloaded. These updates are usually security fixes and should be installed immediately. Java, Flash and Windows Updates will usually appear by your system clock in the lower right-hand corner of the screen.

Hard Drive Diagnostics – Run Check Disk monthly to check for impending computer hard drive failure. Right-click the C: drive and click Properties, click the Tools tab, and then the Check now button within the Error-checking section. Have Windows Automatically fix file system errors and Scan for and attempt recovery of bad sectors.

System Recovery – Despite all of your efforts, your PC will gradually slow down. If you do not have a Windows installation disk, you should burn the recovery disks for your major brand name computer and put them in a safe place. Your Dell, HP, Sony VAIO or Acer computer will have a utility to create these disk. Use them to wipe and restore your computer to factory settings once a year. Your computer will run like brand new. Backup your data first.

Computer Maintenance Checklist For Hardware

computer maintenance checklistHaving a computer maintenance checklist is essential whether you’re a computer repair technician or just a user that needs to be reminded of essential PC maintenance duties. If you are a technician, the checklist tells your client that you’re professional and thorough. Using a PC maintenance checklist as you go through the list helps ensure your computer is getting the preventative work it needs to stay in top running shape. The computer maintenance checklist below is meant to be followed in order, starting with the hardware and working your way into the Windows Operating system.

Before you begin, you’ll want to take note of the computer’s surroundings. Is it in an enclosed area? Is it sitting directly on the floor where it can pickup hair, dust and other debris? Is it sitting in direct sunlight or in an area that can experience extreme temperature shifts? If this is a client’s computer, explain the importance of keeping the computer in a clean, temperature controlled environment.

  • Check to make sure the computer, monitor and printer are all plugged into a surge protector.
  • Take a moment to jot down all makes, models and serial numbers of the computer components so the client has them in case a repair is needed or there is some other type of emergency.
  • Wipe down the monitor, keyboard and mouse with cleaner specifically used for this task. An example would be these alcohol-free screen wipes.
  • Flip keyboard over and shake out debris. Blow out keys and mouse using canned compressed air.
  • Clean external intake grills in the front and in the back of the PC with compressed air. Be sure to get the power supply grill and exhaust fan.
  • Unplug and open the case. Use a computer vacuum or compressed air to remove dust and debris from internal fans and case.
  • Check connections to devices, make sure cables provide unobstructed airflow.
  • Clean optical drive using a CD / DVD lens cleaner.

You want to be careful not to cause any problems when performing computer maintenance on hardware. Moving a PC around, not properly grounding yourself, or causing damage to a wire or card can all cause problems that did not exist before.

Computer Software Maintenance Checklist

Now that the outside of the case is clean and the PC is running cool, log into Windows using an account that has administrative access. By performing the following software maintenance, you can be sure Windows will be secure and optimized for speed.

  • Run Windows Update if the computer is not already configured to obtain these updates automatically.
  • Update virus definitions or install an antivirus if the computer needs one. Our free recommendation is Microsoft Security Essentials.
  • Locate and remove old programs or trial software.
  • Update web browser to the current version.
  • Clean browser temp files. In IE, open browser and click Tools, then Internet Options. Under the General tab, click Delete under Browsing History for more options.
  • Run Disk Cleanup to remove temporary files and empty Recycle Bin. Start>All Programs>Accessories>System Tools>Disk Cleanup.
  • After Disk Cleanup, run Disk Defragmentor from same location.
  • Backup data–pictures, movies, music and email to an external device.

Technicians should always perform this maintenance on new client’s machines upon first visit. Home users can run this checklist monthly. Having a computer maintenance checklist is an essential way to make sure you are doing all of the things necessary to keep your computer secure and performing at peak speeds.

pdfFor your convenience, we’ve created a PDF of this computer maintenance checklist for you to print out and use. Download the computer repair checklist.


In Conclusion, your computer is machine destined to fail. Make sure you know how to obtain and run diagnostics on your computer when that time comes. Use the above methods to run computer diagnostics and if your computer does not have that capability, find a way to obtain a Windows boot disk necessary to run them.

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