Amigamerlin's drivers for WinXP, specifically 2.5 SE, seem to be the best ones out for a Voodoo5 user.
http://www.voodoofiles.com/9488
I think we can all agree that 3DFX's FSAA was probably the best ever implemented into hardware. I decided to chance on picking up one of them on ebay for installation into an arcade machine which has been running on a Voodoo3... it's a nice card, but unfortunately has two strikes against, one that it doesn't have FSAA in hardware, and two, that unofficial driver support for it is quite lacking compared to the more advanced Voodoo5.
I'm personally installing my Voodoo5-5500 for use in a Win98SE arcade machine (for that, I'm using the Amigamerlin 2.9 Win9x drivers) since I'm hoping to be able to make use of Glide for emulation, particularly N64 emulators which use the Glide64 plugin. I'm predicting that the FSAA 4x would be absolutely beautiful since there are so many awful jaggies in N64 games... since I'll be running it at 640x480, no higher, the video card will provide sufficient power for years to come. I'm also hoping for a visual quality improvement in GENS, ZSNES, and the emulator I use most, MAME.
The Voodoo5 isn't so great for modern-day games, but the amigamerlin drivers I've pointed out apparently enable Open_GL (forget D3D) thus allowing games like UT2k3, WC3 and GTA3 to actually run... RoN might be a little too new, though amigamerlin is going to be releasing another update very soon which should be a significant improvement. When that fails, try the WickedGL drivers, I've had some success with them. A word to the wise: don't install DX9, it's actually recommended that you use DX8.1b with the Voodoo drivers.