Weird 3D video problem, weird textures/colors

Hi all,

Since I came back from University, I've been using my old computer to play games, but when I play any 3D game, the graphics are all fuxxored.

The colours are all random and keep changing, and the textures are blurry and cracked. The same thing occurs when I run DXDIAG in Windows and run the Direct 3D tests.

Things I've done:
1) Installed latest drivers
2) Tried every combination of in-game display settings
3) Tried every combination of windows display settings
4) Formatted and re-installed windows
5) Bought a new GeForce card. (I was planning on buying one anyway.)
6) Installed latest DirectX
7) Tried all the above on a clean system immediately after a format

FYI, my system is:
- 1 GHz Intel Pentium III
- 256MB RAM
- Old card was a GeForce MX 100/200 (32MB), new card is a GeForce FX 5600 (256MB)
- Windows XP Home edition/Windows XP Professional edition (same problem under both)

And the games I've had this problem with are:
- Microsoft Flight Sim 2004
- Homeworld 2 (Interestingly, the original Homeworld works fine)

I'm no newb, but I'm about at the limits of my experience and knowledge with this problem. Has anyone got any suggestions regarding this?

Many, many thanks.

Linux.

doesn't sound good - off the top of my head, it's one of these problems:

- fried video card
- fried agp slot or motherboard chipset
- maybe, maybe a bad psu (probably not)

but check this stuff first:

- does your video card require two plugs from the power supply?  have you checked to be sure both plugs come from different wires from the psu?
- can your psu handle what you have hooked up; check here - http://www.jscustompcs.com/power_supply/
- check your computer's temperature and video card temperature if the drivers let you; is it running too hot?

more stuff you could check:

- is it like an 8x AGP card in a 4x slot?  i wouldn't think it would cause problems but maybe it does.
- check in your bios for vga palette snooping and if it's on, kill it.
- try video card in another pc

hope that helps.