If you have a desktop you do not want accessed through the RWW portal there is a simple way to do this. You add the computer name to the “ExcludeList”.
This applies to SBS 2003 not SBS 2008 (see Andy’s comment).
It is a subkey in the Windows Registry found here:
Under this you will see a String Value ‘ExcludeList’
You should add desktops with no spaces and separating multiple names with a comma: