Why won't my Pc play video (Stan Def, not full-screen) or ANY PC games without crashing?

Sounds like it's either overheating or a memory error. Go buy a can of compressed air and clean out your fans with it, then run a memory diagnostic from here: a href="http://oca.microsoft.com/en/windiag.asp" rel="nofollow"http://oca.microsoft.com/en/windiag.asp/a