The upgrade of Windows Server 2000 or 2003 proceeds in more or less the same way as the upgrade process for SBS 2000. To prepare for the installation execute all the steps described in the section Upgrading Small Business Server 2000.
However when upgrading a Windows 2000 or 2003 server you must keep in mind the role that this server is to play in the network as the SBS 2003 can only form one domain which must also be the root domain. If, for example, the server to be upgraded is the domain controller of a subordinate domain, you can definitely configure this for a new domain, but no trust relationships to other domains can be set up with the SBS domain.
This step proceeds exactly as described the section Upgrading Small Business Server 2000.