Sometimes when you don’t need a service on your server, especially on SBS it’s a bit tricky since everything is embedded in the installation. One may notice that you might have a repository of more than 10Gb without knowing and here’s how to stop it. For Windows 2003 server, you might do the following to have a clean stop of the WSUS (Windows Server Update Services) service.

Stop the Update Service from the services.msc or from Administrative Tools/Services
Also set the service as disabled.

Also you might look into the Group Policies for your OU (Organizational Unit) so that the PC’s are not pointing to the server for Windows Updates. Open the Group Policy Management from the Administrative tools or just run gpedit.msc and check if the update service location is set. Remove if specified.

Computer Config -> Administrative Templates -> Windows Components -> Windows Updates -> Specify intranet microsoft update service location

This should stop the WSUS service from running. Also you might either remove or archive the files in the WSUS repository to free up some space.