Random screen reset during games

[ComputerNoob]

I have a Gateway PC.  I got it new about 1.5 years ago.  Here are the specs:
Pentium 4 2.0 GHz
256 MB DDR RAM(DIMM)
Intel 82845G/GL Graphics Controller
Windows XP Home Edition
I just installed the nVidia GeForce4 MX 440 with 64 MB.  Games are running smoother but when I play Unreal Tournament 2003, the screen goes black after about 20 minutes of playing.  It then changes to lighter and lighter shades of gray.  Then, it goes to the desktop and I have to maximize UT2003 again.  Why does it do this and how can I fix it?

[merlin]

maybe a patch is needed>http://www.unrealtournament.com/  also type dxdiag in the run box..or is it getting to hot for the graphics card and therefore its breaking down...

[ComputerNoob]

I downloaded the patch but then the files of UT2003 were corrupted and the game would not run.  I then uninstalled and reinstalled it.  I do not have the patch and the game runs fine.  The screen seems to turn black and go to the desktop every 20-25 minutes.  It may be that it is getting too hot because my PC does not have a fan, except for the 2 inch one in the power source.

[gb johnson]

it may help if you took the case off..more air more cool or have you got  a portable fan place this near your pc any better..

[ComputerNoob]

I think it may just be a combination of overheating and low memory.  If I put a little portable fan near the PC, should i put it so that it faces into the ventilation holes?

[Raptor]

I doubt your computer is overheating. Considering your system specifications.

Unless you are heavily overclocking.

What other games randomly reset? Unreal Tournament 2003 is perhaps above the specifications your system meets.

I suggest you install the later drivers for your Nvidia videocard.