You can change the default programs in any Operating System. This is also called File Association. If you have a .mpg file, for instance, it can be opened by a number of programs including Windows Media Player and Quicktime. Invariably, whenever you install a program such as Quicktime, it will take over the file associations for every type of media it can play. This can be frustrating, as it isn’t always trivial to change them back to the way they were. Windows 7 makes this easier.
Change File Associations in Windows 7
You can change the default program for files by going into the Control Panel and opening Programs. From here, you will select Default Programs and wait until the the left column is populated with all of the programs you have on your PC. Simply select the program you like to use and click Set This Program To Default when it appears in the right-hand column. If there is a tick box to always use that program, be sure to check it when setting the default file association. Otherwise, the changes you make will not stick.
There are other ways to do this, but in Windows 7 this is the easiest. If you had another version of Windows, you can try holding the SHIFT key while right-clicking a file and select Open With. This will give you a list of programs that can be set to open that type of file and there will be a check box you can tick to make it always use that program.
Some browsers will also have preferred applications you can select to open a specific file type. Again, with .mpg files, you might prefer to have Windows Media Player open this type of file by default. So from within Firefox, select Tools, Opetions, then Applications. You can now associate programs to file types.
If you have any problems or questions regarding file association, feel free to ask.