OK, so I don't normally ask for help but I'm at my whit's end here. I was given this laptop to refurbish, from a business that was cycling out old hardware. When you power on the laptop, it loads the BIOS just fine, and everything looks normal. However whenever you try to boot into something, Windows 10 Setup Disk for example, it will start just fine then randomly freeze and power off. Like when a cable is unplugged on a desktop computer, it just kills itself. Does this with Windows 10 Setup, Memtest86+, etc.
I first replaced the power connector just in case, then tried another AC adapter that I know works on another similar PC. Nothing. I then took the whole thing apart, removed the heatsink, and applied new thermal compound (Arctic Silver 5) to the CPU. After putting it back together, it almost seems worse. The application of the compound looks fine, and I've redone it TWICE just to be sure. I'm not sure where to go with this next, help would be appreciated.