Hmm, first, that's a VERY low 3D Mark score in my opinion. With a non-overclocked GF4-Ti4200 and a Athlon XP 1700+, i get a little more than 9000! Sure, 1ghz CPU is low, but that score, says locking is not your only problem - there's more than that.
1. In your BIOS, you *are* activating AGP and not PCI, right? And you ARE activating the highest AGP setting you can ( 2x or 4x, not sure what it is on your motherboards )
2. Are you enabling AGP fastwrite? If so, you could try to see if you still got the problem without it. If you didn't activate it, activating it shouldn't make the problem bigger. Also, if you aren't doing so, it might be a good idea to activate Side Band Adressing to increase performance.
3. You DID uninstall the Voodoo 3 3000 drivers correctly, right?
4. Did you install the latest Detonator drivers?
5. Also, "Graphic Win Size" or "Aperture Size", names depend on BIOS, is activated? If it isn't, activate it. If nothing else works, try disactivating it.
You might want to try flashing your BIOS, who knows... don't have a lot of ideas, it's a pretty odd problem.
If REALLY nothing works, your last chance might be formatting your HD and reinstalling windows. But before that, you better see if anyone else got ideas.