On a Windows SBS 2008 server, you can easily experience huge issues with data filling up the system hard drive.
If you look closer, you will probably see that there is one folder which is constantly growing up : WsusContent.
This folder is used by Windows for the system updates, but it can be moved without troubles using the wsusutil tool.
Open a DOS command on the server and move to the WSUS directory:
C:\Program Files\Update Services\Tools
Now to move WsusContent, run the following command:
wsusutil movecontent <path to your new WSUS directory> <log file>
wsusutil movecontent E:\WSUS C:\log_movecontent_wsus.txt
This command will create UpdateServicesPackages and WsusContent directories in your new WSUS location, and copy their contents.
Once it's done, you can remove the old directories.