Computer freezing

[mysteryman]

Had this pc I built about 2 and half years ago. Everythings been fine but recently I recieved a blue screen with a IRQL NOT LESS OR EQUAL error message on Windows 7 beta edition I was using. So I switched back to Windows Vista thinking that the OS was the problem. Now the computer freezes and the screen just freezes up and I have to keep resetting. This may happen after an hour or half hour but seems a bit random. I've checked for viruses, malware and spyware in the memory but found none. Does anyone know what the problem could be? Thanks

 

[J.B]

Sounds like you could have dodgy RAM, try running just one stick at a time, and in different sockets.

Also try running Memtest