If I purchase a server 2003 system builder cd can i use it to upgrade a server 2000 system?

Yes, you can, I am assuming by system builder you mean w2k3 OSIsaac Oben MCITP:EA, MCSE

Yes. Here is a document which provide informaiton about upgrading Windows 2000 to Windows 2003. Upgwin2k.doc - Upgrading from Windows 2000 to Windows Server 2003 http://download.microsoft.com/download/9/9/6/996f17f2-e008-4581-a26f-9098f87690e2/Upgwin2k.doc And if you would like to upgrade Windows 2000 domain, here is an KB article for reference: Common Mistakes When Upgrading a Windows 2000 Domain To a Windows 2003 Domain http://support.microsoft.com/kb/555040Shaon Shan| TechNet Subscriber Support in forum| If you have any feedback on our support, please contact tngfb@microsoft.com