Supplement One of the Windows 2000 Server Resource Kit contains MSSizer:
"This GUI tool estimates the hardware requirements for deploying Active Directory based on an organization's profile, domain information, and site topology.
Based on user input and internal formulas, Sizer estimates the number of the following hardware requirements:
Domain controllers per domain per site
Global Catalog servers per domain per site
CPUs per machine and type of CPU
Disks needed for Active Directory data storage
In addition, MSSizer provides approximate estimates for the following other requirements:
Amount of memory required
Network bandwidth utilization
Domain database size
Global catalog database size
Intersite replication bandwidth required"
NOTE: You must install the tool from the \Apps\Adsizer\ folder of the Supplement One CD-ROM.