Hm....

Help ?

Apart from using the latest Beta Releases and enabling all Tweaks (Guardband clipping etc.), not much you can do.

Try to upgrade to an AMD Athlon System (or comparable), and you'll see a very nice performance boost with that Voodoo4...

But one Tweak you could try on your CPU actually :
Test, and if possible, reduce the L2 Cache latency of your CPU using H.Oda's WCPUl2 Utility.
On my PentiumII-400 in the old days, that got a nice boost out of the CPU (upto 10%).

400 3DMarks (I assume 2001se?) is about right for that system. I got about 550 point with a Celeron 300MHz clocked at 450MHz. And that's with a Voodoo 5

Your other system (the Athlon 1700@2200) should give you about 2500 points.

Hm, a last line of Tweak would be the Motherboard, more precisely the Chipset.

Your mileage may vary, but try H.Oda's WPCRedit and WPCRset Tools.
All Chipset Registers (including all performance relevant) are available for Tuning there (BX Chipset .pcr file is included).

Depends on how far you can push the Timings and advanced Tweaks, but a few more % are in for you if you take the time.

(Advanced tweaks include DRAM Turbo-Refresh, Self-Refresh, Burst length and all kinds of mostly RAM related Chipset Timings)

In the end however, when all is apparently running stable, you should put that to a test, e.g. with Prime95. Otherwise, instability or (worst case) data loss could result in the long run.

Upon launching, just cancel the registration Window, and use the program's "Burn in" or "Self/Stress Test" feature to check for errors on Bit level under full load.

http://www.mersenne.org/freesoft.htm