ReleaseEngineering/How To/Set Passwords On Win2K3SP2
Alt-Ctl-Del (on a mac via screen sharing, that's fn-control-option-command-delete), click "Change Password"
You can't do this from the cltbld account; log out via VNC and log back in as Administrator, then double-click the VNC icon in the systray, and click the "Configure" button under "Authentication".
Run the following command:
Uncheck "Users must enter a user name and password to use this computer" and save.