pc keeps shutting down

[Dygivve]

i bought some new stuff for my computer a few days ago but when i put it together their was a slight problem, when i turn on my computer after a short amount of time it automaticly turns off i have tried upgrading my Power supply from 650W to 800W but i still had the same problem. i also tried putting in my old 7900GT. i have never overclocked anything on my pc

the prossesor, mobo, and case are new the ram was stock with my old HP same with the HDD,the gpu a bought in march. i went back and put my RAM HDD PSU and GPU back in my old HP case and it works fine (BTW i tryed removeing the hard drive and it still shut down after a few seconds so dont tell me its the hard drive)

NEED HELP ASAP UT3 is out tomorrow!!

heres my hardware

GPU: HD 2900 XT
CPU: intel quad Q6600 2.4Ghz
OS: Vista 32 bit
RAM: samsung 2 gigs
MOBO: Gigabyte N650sli-ds4
Case: antec Nine hundred

[nfleming]

Check to make sure the old memory is really right for the motherboard/cpu speed and timing wise.

IF it is you might want to download memtest and give it a go. You burn a bootable CD and then boot into a memory tester, very useful for such things.

Could also be a problem that the CPU cooler is not properly situated on the chip. Make sure the amount of thermal compound is appropriate, not too much or too little.

Also reseat every connector and card (you probably already did that one )

[Dygivve]

OMg ty soos much all i had to do was reajust my CPU fan
silly me didnt have it pushed up against the CPU all the way