Games freeze every 15min

[giant384]

everytime i play games like halo,UT2k4,hl,hl2,cs,cs:s my comp. freezes after 15min of gameplay. this started happening after the steam crash last week and my game files mysteriously dissapeared could this be a hardware or some kind of software corruption

 

[Ames]

Have you tried all the normal stuff yet, i.e., scan for viruses, spyware, defrag, etc?