There are no join options because there is nothing for the HomeGroup to share.
So in this case M$'s joke is - we will tell them there is no homegroup to join, and see how long it takes them to figure out what we really mean is that there is nothing shared to view.
You must have at least ONE share for the join option to appear.
NOW, the reason why there is nothing shared becomes another issue!!!!!!!!
NORMALLY, If you clean install two W7 systems and do the HomeGroup thing they hook right up. There are some folders that default to share with the homegroup.
So I am suspecting the ownership is messed up. This happens if you do an install of W7 then go back and do an upgrade install - actually I can't remember exactly what I did and I...