Connecting a Windows 7 PC with a Windows 8 PC

Networking has been changing with the evolution of Windows.  I doubt that Microsoft has tried to exhaust the combinations of PC's running different versions of Windows in testing their network functions.  Making mutual access between PC's can be challenging.

I have observed that a Windows 8 PC and a Windows 7 PC can discover each other, but they cannot access each other's shared folders unless the Windows 7 PC joins the homegroup of the Windows 8 PC.  Of course, this depends on which versions of Windows 7, Window 8, and their configurations.