I have a ABIT KT7A (no raid) with an overclocked Gainward GeForce 3, and I experienced symptoms similar to yours- very low scores or crashing during 3D Mark, but usually the system wouldn't even boot up at all, especially after i moved to XP.
I originally thought that the overclocked video card was causing stability problems, but i was never able to boot into anything but safe mode to verify it.
I had to finally just find the time to hunker down and do the obvious- flash the BIOS to the latest version, download all the windows XP updates, install the latest VIA 4-in-1s, and of course the latest Detonator...I just did this last week, so I'm using drivers that were current then.
Took a day and a half on my 56K, but it was well worth it, the games started running (flying!) the 3D marks went back up and the system is as stable as you can expect any Microsoft OS to be.
good luck, d.