I have been having problems with my video card since early this year. I believe it was in January when my video first showed a significant decrease in 3D performance for no apparent reason. After much fuss over it, I decided to just reinstall WinXP, which fixed the problem for a week or two. After that time, performance went back down to extremely low levels in 3D applications. After another install of Windows, my performance went kaput again. At that point, I borrowed my brother's Windows 2000 CD to see if XP was the problem, which it wasn't. Later on, I blamed World of Warcraft for doing something to my software behind the scenes, since the problems started occurring when I got that game for Xmas. The last time I installed Windows, I left it off. Well, here I am with very slow 3D acceleration yet again after about two weeks.
On average, this causes games to run well below 20 frames per second (from about 45-60), and causes the cube in a DirectX diagnostic to spin painfully slow. My computer is as follows:
Pentium IV 2.5 ghz
Gigabyte P4 Titan 8IG1000MK motherboard
1024 mb Kingston dual channel RAM
Radeon 9800 PRO 128 with the latest ATI drivers
Sound Blaster Live! 24-bit sound card
120 gb Seagate ATA hard drive
The problem turned out to be the drivers. I don't know if the official divers just suck or what, but I switched to the Omega drivers, and that has fixed it, at least for now. Before, even if I made a clean reinstall of the ATI drivers, the problem would still be there.