After you connected the computers to the network, you should have received a question about wether you wanted the network to be public or private. If you want the PCs to see each other and to share files, you should select "private" (not "public"), which
some people find counterintuitive.
Anyway, if that was not the problem, then instead of asking in the Training and Certification forum you will probably get better answers if you ask in one of the forums devoted to Windows 7 such as this one:
http://social.technet.microsoft.com/Forums/en-US/w7itpronetworking/threads