Computer Black Screen Crash

[Haste25]

I have had this problem for about a year. I have taken my computer to a computer repair place in town but they were unable to fix it. When I play certain games (WarcraftIII,Rome Total War,NWN,ect.), the monitor will all of a sudden go black. This can happen when I first start the game, or an hour or more into it. Turning the monitor off an on doesn't fix anything, and the OS is off as far as I know(no sound, no way to get anything but the black screen) but the power supply is still running.
Some suggestions I have heard are:
A monitor problem(which I don't think it is because I have switched monitors and it still happens),
A heating problem (all the fans are working as far as I know and the system temp is around 23 and cpu 44),
Or a power supply issue (this is the most likely, other than maybe my graphics card just being faulty. I have a 350W, (my brother has the exact same computer as me except for a 300W power supply [his also has the same problem but much less frequent]) and it checks out okay exept that the +12 V is close to the low limit (something like 11.2 when the limits like 11.0).
I don't know what components take +12V so I haven't been able to test that aspect yet.

Here are my system specs:
AMD 2000+ XP
512 DDR DIMM Ram
5600 Nvidia GeForce Ultra AGP (Latest Drivers Installed)
ABIT NF-7S Motherboard
GEM 17" LCD
DVD-ROM/CD-RW
CD-RW
2x40GB HD
Floppy Drive
Windows XP SP2 -Updated
2 Side Case Fans, 1 Ftont and 1 Back
350W Power Supply

Any suggestions are welcome, thanks.

 

[SHAWN]

The wattage on the PSU is low for what you have. You should have at least a 430watt. Also did you try turning off hibernation? Did this start happening after you installed SP2 or before?

 

[Rayne]

Shawn u have the same case as me

As for your problem Haste, try clearing the CMOS

 

[Capricorn]

Actually, I run more than he's got on a smaller power supply. A lot depends on the brand of power supply. But heat and power supply were my first two guesses. Doesn't sound like heat is the problem if your CPU is only 44. (Have you checked that when you've just finished running a game for a bit, or is that 44 at idle/low load?) Got your PC plugged into a good UPS? (Crappy power supplies don't like A/C line variations much either.) Might check that the GPU fan is running and not dirty, too. None of those temps is your GPU temp, so it could be higher.