After you join your Windows 7 pc to a homegroup, you may notice a text file named by the hostname (example: saihari.txt where saihari is the host name of my Windows 7 PC). The contents of the file will be
1.Interfaces on the system
2. Routing table for IPv4 and IPv6
This file can be found under C:\User\ (ex: C:\User\saihari.txt). To stop this file from loading at the startup you can safely rename the file or move/delete the file.
This should help!