I spent 3 days trying to solve why my Windows 7 machine suddenly decide not to see my XP machines in the local network. Tried everything I could find in the question already posted.
None that is listed seem to work, I could see the Windows 7 machines ok. Solve the problem by using a Sabrent USB ultra Compact RJ45 adaptor. Install and put in my IP address and all my network shows up. Didn't know where to put this, but I know from the post someone else is having the same problem. The above machine had been working fine for over a year.