If you don't have these files installed, you'll have error messages or other problems when loading some tracks.
Extract this .rar file to a temporary directory. Then copy the 2 .mas files that you'll find in \Common Maps Patch\Locations\ into your \GameData\Locations directory.
Now it should work.
Patch files for Watkins Glen (or other tracks) 1.0
Problems wit Watkins Glen Track (or other)? This might help!