Garmin Mobile PC is a software program that runs on a computer. If you mean, can you use the Magellan as a GPS receiver to provide data to the computer, then it depends whether the Magellan puts out a standard NMEA signal. As it is a 10 year old or so device, it would be easier if you bought a inexpensive dedicated USB GPS receiver for use with Mobile PC.
I might add that later versions of Mobile PC are not good at finding GPS receivers on real COM ports (the 9 pin-type connectors on the back of older computers). I just retested mine (5.00.60) with an eMap physically attached to COM 1 and GMPC could not find it. However it did lock onto a BT GPS unit 25 feet away in another room (on a different floor) that I had forgotten to turn off. I had confirmed that the eMap signal was good with GPS Gate.
Terry