If you switch your win7 machine from "Home Network" to "Work network" then enable Network Discovery and "Username and Password" sharing in the advance part of the Network and Sharing applet, you will discover you have XP style sharing, which is a lot more capable than Homegroups.
1) make sure the "Computer Browser" service is running.
2) If you are going to rely upon network enumeration (that silly green bar when you open the network folder) it may not work on different workgroups or sub nodes of the same network. The fix is pretty simple... in the address bar at the top of the network explorer (NOT the search bar) type the name of the machine you want in UNC style. eg. \\Falgar and hit enter. Once you confirm that you can access the machine, just make a shortcut to it. I have a folder in my User folder called "Net Links" where I have my entire network mapped out as shortcuts. This way I don't have to wait the sometimes 10 to 15 minutes for windows to discover things on it's own.