First of all make sure you have latest VIA 4in1 drivers installed, depending which motherboard you have.
If its amd+via board you have to install only amd agp driver and the rest from via 4in1.
Secondly your problem is your CPU - sorry but its true.
You need at least 1 Ghz processor to take a full advantage of the geforce3 (actually it becomes limited around 1.4Ghz)