I placed the DWORD value "Advertise" (no quotes) in
and set it to the value 1. This seemed to successfully work around the issue I've been having with the NETBIOS names of my home Windows 7 PCs randomly appearing and dropping off of my Mountain Lion finder list. Please note that this setting appears to advertise the computer's description (from Computer Properties), not the computer's NETBIOS name.
All of the usual disclaimers regarding editing the Windows registry apply here, of course, and your mileage may vary, but I hope this is the answer you were looking for.