Pc freezing?

Hey all, turned my Pc on tonight and starts up, goes into SL 15 minutes later it freezes, ALT + DEL and the usual no response, had to reboot, this happened three times, checked all wiring cleaned fans ect, I have'nt changed anything or added anything recently. If I leave machine running its fine? Never had any problems since being in SL (01/01/06) before getting into SL I used to play BF2 and ran server control software (bf2cc) and all was well? which is just as if not more intensive as SL.

specs

P4 3.0HT
1024meg ram
rad 9500 with latest OMEGA drivers

I noticed on last crash FPS was a bit erratic and dropped to 17 then crashed, any help would be appreciated thanks

Actually when it comes down to actual cpu cycles, SL is more intensive because more work is being done. All your maps and everything in BF2 are stored as static meshes stored locally on your harddrive. Everything is streamed in SL and can't be converted to mesh form.

Anyways have you tried setting the affinity for SL on one of your virtual CPUs? Also, when was the last time you ran a virus scan/spyware remover? Have you tried uninstalling & reinstalling? Also, did you clean out your old videocard drivers with a program like Driver Cleaner Pro before installing the Omega drivers?

Sorted, tiny hands had been at the keyboard lol, somehow managing to tick a seperate ATI tray in msconfig, I thought it was strange cos as I say nothing had been added or changed since well before Christmas, I only thought mentioned about bf2 cos with SL I can have photoshop msn yahoo anti virus ect ect runnin at same time and had 50% cpu free, where as BF2 you'd have more chance winnin the lotto (although it is the wonderful EA)