Have a look in services. Start menu search box, type services.msc, hit enter. Ensure that the IP Helper service is set to auto and running.
If it is and you still need help, please open a command prompt. Copy and paste the following, then hit enter. Post a screenshot.
ipconfig /allcompartments /all
If you don't know, Homegroup only works between Windows 7 computers and no other operating systems. You can share drives or folders classically if you have Vista, XP etc... on another machine.