Windows 2000 Professional supports 2 CPUs and 4 GB RAM.
Windows 2000 Server supports 4 CPUs and 4 GB RAM.
Windows 2000 Advanced Server supports 8 CPUs, 8 GB RAM, and for Clusters 2 node failover and 32 node load balancing.
Windows 2000 DataCenter Server supports 32 CPUs, 64 GB RAM, and for Clusters 4 node cascaded failover and 32 node load balancing.
Check also www.microsoft.com for more details.