I would say this is a rather interesting bug.
OS: Windows XP (32-bit) SP3
If you create a rule to block nvsvc32.exe (NVIDIA Driver Helper Service 266.58) then you cannot access any of the computers on your LAN using Windows Explorer even if they are in your network map as "Shared".
If you delete the rule and set Program Control to Automatic, when you access your LAN via Windows Explorer (My Network Places) then NIS will create a rule for nvsvc32.exe for the following:
UDP on ports 137, 138
TCP on port 139
This will then allow Windows Explorer to access other computers on the LAN.
Oddly, NIS never creates rules for explorer.exe which is the program that should have rules since it is the one that is accessing the network.
Please fix this issue. I should not have to allow my video driver access to my LAN in order to browse other computers.