A freqently asked question on the newsgroups is: "How do I prevent certain computers from showing up in the list of computers when using RWW?".
Well, Microsoft's TechNet provides a list of registry keys/values that can be modified via Regedit here: Click here
Wayne Small provides the specific answer to hiding certain computers from showing up in RWW here: Click here
1. From your server, run Regedit and go to HKLM\Software\Microsoft\SmallBusinessServer\RemoteUserPortal
2. From the Edit menu, click New > String Value
3. Give the string value a name of ExcludeList (with no space) and press Enter
4. Right click on the new field, and select Modify
5. Add the names of the machines you wish to hide, spearated by a comma.