Strange graphical errors in some games

Hi. I have a problem with graphical errors in some games. For example neither NHL nor FIFA series of games work (original games, no warez). At first i thought it had something to do with EA:s engine but recently I've experienced the same problem in other games. It's hard to describe the errors but some polygons have no texturing and it seems like z-bufering doesn't work either.
So far only DirectX games have had these errors, no OpenGL ones.

System specs follow:
Motherboard - ECS K7S5A
Gfx-card - Geforce2 MX (don't remember brand)
soundcard on the motherboard.
Win2000 SP1

So what have I done so far to get rid of the problem?

Upgraded BIOS on the motherboard
Tried different detonators (latest I've tried is 30.xx)
Installed DirectX 8.1 and run dxdiag. No errors.
Tried with another Geforce 2MX card. Same problems.
Formatted and reinstalled Win2k.

At first I thougt the problem was that the MB had Via chipset and needed VIA 4In1 but it turns out it has a chipset from SIS (SIS735).

Hope someone can help