I just upgraded to Git 1.8.0.1 for Windows, from my previous version 1.7.9.mysysgit.0. I downloaded the new version from the Git site and installed through the normal Git in
to check out your PATH variable, act as follow:
Once there, scroll to get the Path row, you'll get a long string of paths (e.g. C:\windows\bin;C:\program files\git, etc)
Find the line or lines where git is referenced. Then, make sure this path point to your Git 1.8.x installation. If not, delete it and add the real path to the newest Git version. At the end, you should only have one path in the string linking to Git.