I'm aware this is an oldie but posting here to see if anyone has any remedies.
Been on the net all evening trying to find out why the Mac (Snow Leopard) will not see Win7 on the local network.
Works fine the other way so I can still copy stuff back and forth from the PC, but curious.
(Oddly, it used to work with Vista
but the last time I used it the Mac had stopped seeing Vista - before Win7 - so maybe its not Win7, or could be a coincidence.)
Anyway, now, avoiding the Win7 'Homegroup' altogether (after few days of failing to make it work), and trying to do the old Workgoup thing, I finally followed this route using IP addresses to get them connected at all -
http://www.trickyways.com/2011/07/file-sharing-mac-os-x-lion-and-pc-windows-7/Yippee... But still didn't get the Mac (SMB) to see Win7 at all.