SBS 2003: Installing Windows 7

If you want to use http://servername/connectcomputer to join a Windows 7 (download) machine to your SBS 2003 domain you must first install hotfix KB926505. Most SBS 2003 installations should already have this update installed as this is the same hotfix that allowed Windows Vista machines to join the SBS domain using the ConnectComputer website.

Source:→ SBS blog