Computer groups are created in WSUS to manage computers and deploy patches in a more controlled fashion. However, to add computers to your computer groups you need to configure either Group Policy ...

I have a Domain and a WSUS instance at home. There are two computers that I've removed from service, removed from the Domain, and removed from WSUS, but they reappear in WSUS after a short time ...

After that, the WSUS console will show that computer. I believe you may need to assign it to a group in the registry as well.

Creating groups is simple. Open the Windows Server Update Services management tool, then expand Computers, right-click on Unassigned Computers, and select Add Computer Group.