Solved the Homegroup trouble with Windows 7 computers.
Here is what I was experiencing two of the computers on my home network are Windows 7 and two more and Windows XP Home. All of the computers would show up in the network listing under Network. Though when I'd select the homegroup on either on of the Windows 7 machines no matter what they would list only create homegroup.
I bought the family upgrade and when I installed the OS on each of the Windows 7 machined during the install I created the homegroup so both of them created the password. All manner of leaving did not do anything. I read where the windows firewall was certified to work with homegroup. I have comcast for an ISP so I use McAfee for security including the McAfee personal firewall. So I tried to turn off the firewall and use the Windows firewall. Couldn't do it. Thought that the firewall in the Router was causing a problem so turned that of. Didn't help.
So I created a homegroup in one of the Windows 7 machines. Left the homegroup in the other and went about removing the firewall on the second one. Did that and still did not allow for a homegroup connection. The second machine would only list Create Homegroup. Not the Join button. Thought that I would give up and wait until MicroSoft figures this out. I set to reinstall the McAfee security D/L'd it and set it to install.
Once it was done checked the homegroup and there was the Join button. Once done I went back in to the Router setup and enabled the router firewall and all is still well.
Hope this helps someone.