I just spent an entire day figuring this issue out.
Nothing solved it for me.
I have a dual LAN on my computer and two computers with Windows 7.
One Lan card is for internet and the other is for connecting via ethernet cable with the second computer. I can share internet and files with the two but I can't make the remote computer to join the Home group since it is connected to the unidentified network LAN card on my host computer.
How can I change the unidentified network to Home? sine it is actually home!
I configured static IP in order to share the internet and enabled the ICS.