I also have an old P-600 desktop featuring a Riva TNT2 M64 which is only supported by the 71.x driver family. Unfortunately the driver no longer works in Ubuntu 8.10. Please help Ubuntu developers by providing a new compatible driver, they will be happy to package it ASAP.
Seeing how windows are redrawing is really a pain
For now the only solution is to stick with nv.
P.S. I currently have no resources to buy a more expensive card and proceed with the upgrade.