if you have NT detecing two processors,
run quake, pull down the command console and type in
R_SMP 1
you will have to quit the game and restart it but next time you go in it should run in SMP mode. (To test, type again at the console R_SMP it should come back with a value of 1)
BTW Some people claim that Voodoo cards are not very stable in SMP...
Good Luck