The *.GMAP directory (is where the mapsource files are located on your PC) and by default are on your "C" drive in specific locations under different operating systems. Default locations are:
XP - C:\Documents and Settings\All Users\Application Data\GARMIN\Maps\(gmap dir here)
Vista and Windows 7 - C:\Users\username\AppData\Roaming\Garmin\Maps\(gma p dir here)
You can actually move the entire gmap directory to any drive and directory you like and Mapsource will see them IF you simply put a "link/shortcut" in the default location which points to where you have moved the files.
You can also use any name you like. You don't necessarily have to use the same top level name used by Garmin.
This was tested only with Mapsource 6.16.3 and I don't know about compatability with older versions.
Last edited by Tiger; 24th June 2011 at 22:01.
Reason: additional info and correctons
Re: How to Move the GMAP dir to an alternate location
Another method is to use JaVaWa GMTK from JaVaWa GPS-tools | JaVaWa GMTK. This software also allows you to backup and restore your maps to another machine and tests and can correct errors with the map installation.