Have you tried setting the env vars just as nasty wrote above?
BTW Mediator/Warp3D should be set to No (if I recall correctly it's supposed to be set to Yes only when using Voodoo 4/5), and Warp3D/Mediator/MemSize to 7.
Also, make sure you close every window and turn off your WB backdrop (if any) in order to save some video memory.
