Garmin Mobile PC works similar to Mobile XT. Just drop the gmapsupp.img and gmapbmap.img including the gmapsupp.unl in the main directory and it works.
I like to add that there is a company named Symarctic (google around) that developed a freeware program (jar) to let the GPS built-in module from a Nokia N95 phone work as the external GPS receiver for a pc.
As I don't have a N95, I gave it a try with my Nokia E71-1 in combination with ...........Garmin Mobile PC, and .............IT WORKS.ExtGPS is a java based app that allows a bluetooth connection to be made with an S60v3 device to act as an external GPS for Mac, Windows, Linux and other S60 devices.
Good luck.
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