Computer powers down during gameplay

[jpfan18]

Hi I have a custom built rig that more than enough meets the req for most of the games in the market.

Athlon 64 3800+
512 7900gt
2 X 250 GB Hard drive
2 gigs of ram
550 psu

When I first built it I played Hitman, Ghost Recon Advanced Warfighter, and Oblivion all on high settings with NO problems. My problem began recently when I installed FEAR. My pc powers off whenever hit play on the start menu. I checked the system req. and it doesnt say if it supports my graphics card or not. I would think that it would since it is newer than all the ones it supports. Then I installed splinter cell double agent. It plays on my computer on high settings but it lags and I get the occassional power off every now and then. Today I installed Battlefield 2. I cant go 15 minutes in the game without my computer shutting down on me! Its really frustrating. My roomate is telling me that it could be my psu but "pc wizard" is telling me that my voltages are fine. Why is it that ghost recon and Oblivion run flawlessly on my computer and BF2/FEAR wont? Could someone help me? I'd really appreciate it ty

 

[gmanych]

I have had some restarting issue's, it seems to be for me. SP2 and P2P applications... it weird, when i install either SP2 or a P2P file sharing program my computer restarts...

 

[Instrumediatech]

Overheating?

 

[SYL\X/3K]

wat are ur temps for ur cpu?

 

[jpfan18]

I'm pretty sure my temps are fine. My gpu gets to around 63 degrees. What I dont get is that oblivion and ghost recon are both more graphics intensive, yet they never crash on me... With BF2 even with the graphics on low and medium the game still causes my computer to power down.