! I only seem to have a low framerate here <= 11 (even without frame limiter ) on a P4 2667 Geforce 4, 512 MB.
New-ish Detonator drivers have royally ****ed up DirectDraw performance -- to the point where I think that nVidia should have apologised and withdrawn the drivers. In most cases, DDraw performance is pretty much unusable. Try reverting to older drivers (30.82, if I remember the version number), which don't have this problem.

Of course, I took the simple solution and bought an ATi when I was due for my usual tired-of-computer-too-lame-to-play-games upgrade.