Right, I've always had trouble with this shitty graphics card but now I really want to know why....

Basically, when i first built the PC it was running fine, until I tried to play GTA: San Andreas, my PC shat itself after about 10 mins of playing.

I can't remember how I decided to do this but I turned the AGP transfer speed down to 4x instead of the 8x, this solved the problem but completely fucked up the graphics making them look like shit.

I've just bought Test Drive Unlimited and installed it and it doesn't play too well, so I decided to try it at 8x again, rebooted the PC and it crashed and restarted itself (got stuck in a cycle), I couldn't even get as far as turning the AGP speed down in windows (changing it in BIOS didn't help) I had to boot in safe mode and do a system restore.

So does anyone have any ideas as to why it likes to shit itself at 8x?

I have an Athlon 3000+ 1.8Ghz running at 2.1Ghz
1GB PC3200 DDR RAM
ATI Radeon 9550 Graphics Card

Thanks for any input