Doom 3 Demo Crashing

[unic]

I downloaded and installed the Doom 3 demo, wanting to have a look at it, even though I doubt it's really my type of game.

However, it keeps crashing. Not to desktop, but hard crashes, freezing up the whole computer so I have to reboot it. It crashes before the end of the introduction cut scene, or if I skip past that, within a minute or two of gameplay...

I havn't been able to figure out what the issue is, and have run out of ideas what to try next, and came here to ask for suggestions.

My system is:
Operating System: Windows XP Home Edition (5.1, Build 2600) Service Pack 1
Processor: AMD Athlon(tm) XP 2100+, ~1.7GHz
Memory: 512MB RAM
DirectX Version: DirectX 9.0c (4.09.0000.0904)
Graphic Card name: NVIDIA GeForce4 Ti 4200
Graphic Card Driver Version: 6.14.0010.6693 (English)
Sound Card Description: Avance AC97 Audio

I have tried upgrading my graphic card drivers, running with sound deactivated, shutting off firewall and antivirus, and nothing seems to make a difference - it invariably crashes right at the start of the game.

Any suggestions what to do? I googled a bit, but didn't find anything more than what I had tried above.

[KingB]

Make sure that your video card has its own IRQ and not sharing with too many other things. I was having the same problem until I realized my video card was sharing with about 6 different things. Hope thats it.