When I first got my new computer (~year and half ago) I got a 64-bit dual AMD processor put in; because of this my dad thought it'd be a good idea to put Windows XP x64 on my computer. At the time it wasn't even retail available, which is usually not the best time to buy software, but whatever.

As soon as I got it, I noticed some strange things. It was fast, for sure, and it was solid in the graphics department. But some games just didn't work well - most notably, the Star Wars: KOTOR series. When you turn the computer on, the games all run just fine, but over time (~25 minutes, sometimes much less or much more) they begin to break down; missing pixels, skipping, and things that effect the game's very engine - like a 25-second ability lasting twenty five minutes, for example. Another game heavily effected were my EA Sports games, and my Rome: Total War game.

Newer games seem to work fine, for the most part - they degenerate a bit over time but are mostly playable.

When I try and run a compatibility check with my SWKOTOR games, it always tells me that my graphics drivers are not installed, despite having the very latest nVidia 64-bit drivers on... I've uninstalled the drivers and re-installed from scratch and it makes no difference. It might not be a strictly 64-bit-related problem, so here's my graphics card specs:

nVidia GeForce 6600 GTx2 joined by a bridge, I assume.

Geeks, what I'm asking is - is there anything simple that I'm doing that could fix this? I'd rather not spend 400 bucks getting it looked at, and I'd also rather not just uninstall windows and go back to regular XP... if you need any more information I'll be happy to provide.