Sounds like you need to spend time with Microsoft FixIt
IF that fails locate your Windows7 installation disc
and run a "Windows Repair" on your Windows7 Pro machine.
there is one glitch I discovered with Homegroups, if a homegroup is created
with a particular computer and you are trying to delete that specific homegroup
all other computers or devices (Wired or wireless) that are members of that
specific homegroup must be shut down or "offline" or any attempts to delete the homegroup will fail.