Well, recently I've been looking to get Counter Strike: Source, Garry's Mod, and Call of Duty 2. So I just wanted to post this for people who might wanna know if their computer can run these games. I know this works for Windows Vista, and probably for Windows XP, but if someone can verify that, I would appreciate it.
- Go to Start>Run for XP, and for Vista, go Start, and then search "run" at the bottom.
- On Run, type in "dxdiag"
- Yay! You now have all your system diagnostics!

It should look something like this:
Hope this helped someone.