My Windows 7 PC can find my Mac but can't connect to it. No password prompt?
It is likely just authentication issues.

On the PC RIGHT-Click on the computer icon and select Map Drive. Enter the path name (I'd use IP address but hostname might work) like this:

\\192.168.x.x\[SHORTUSERNAME]


Use the Mac's IP address, then a backslash and then the short username of the account you want to connect to.

There should be a checkbox for "log on with different credentials." check that

You'll click done (or OK, I don't remember exactly) and the PC will prompt you for a username and a password. Try the username and password of the Mac. If that fails try the fully qualified username, which includes the hostname (computer name) of the Mac, a back slash ( \ ) and then the username on the Mac, followed by the password. That usually works for me.