urbantechie,
Windows 2000 DataCenter is the best... the mother of Windows 2000, but you can't buy the OS. It can only be purchased from a few selected vendors (Compaq, Dell, etc.) when you're ready to buy their server(s). Microsoft is trying to limit the hardware support to a small number so DateCenter can more stable under a control environment. Just like UNIX, you can't buy UNIX directly... you buy it along with the server(s). It's a good strategy to compete against UNIX.