I'm not familiar with adapting mini PCI to PCI, but the main issue you'll run into is that a laptop's display can only receive a signal from the internal graphics chip. If you added a Voodoo 3 it'd have to be attached to an external display, as well as an auxiliary power source (notice that it says it needs a 4 pin "hard drive" power connector either from a PC power supply or another source).

Keep in mind they run very hot with stock cooling and they're quite expensive (expect to pay $100-$150 right now for a PCI V3). If using one of those adapters would actually work and you don't mind using an external display, a Geforce 2 MX PCI of some kind would probably be more suitable.

Oh hai, I did a whole thread on this a while ago. I was using docking stations with PCI slots, but the principle's the same.

One caveat in "modern" laptops with mini PCI-e slots is that the manufacturers like to "whitelist" devices in the slot so you can only use it with e.g. certain wi-fi cards or whatever. I'm not aware of any of them doing that on old-PCI back in the Win98 era though. YMMV.

If you want to go 3DFX, a Voodoo2 would be a good solution - you can run the desktop on the internal GPU, and games on an external monitor attached to the 3D card.