Not sure about Win2k, but I got 3 cards working on my laptop running Win98 awhile ago.
Builtin AGP 8mb card, 2 pci (matroxG200 and some Diamond 4mb card) in the docking station.
Only problem I had was sometimes it would lose the virtual desktop setup....kinda annoying, but fine long as I didn't shut down.
I think multi-monitor is supported in Win2k...not sure though.
EDIT: Oh yeah...some video cards don't work well with others....it's kinda a gamble.