My friend recently bought a OEM X800 XT PE from Evesham as an upgrade to his system (specs below).
Packard Bell
Intel Pentium 4 2.8 GHZ
1GB crucial value (upgraded)
Some Micro ATX mobo
480W PSU
and obviously the X800 Xt
Sorry the specs are a little sketchy but it's not my computer.
Anyway, the story is that he bought this card and found several problems. Some games like Rome: TW don't run at all, Doom 3 loads and then jumps back to the main menu, Far Cry has some yellow textures and HL2 runs at just 50 fps. At the time he had a 250 W psu which he just upgraded (assuming that that was the prob) but he was more than a little pissed when that did nothing. My first guess is that the RAM might be playing up, but thats just from my very limited technical knowledge, I'd be sograteful if anyone could give me some more ideas.
Oh, I almost forgot to say before he ahd a 9000 pro which worked but now it doesn't too. That's why RAM jumped to my mind because of the loading.