MAKE BACKUP YOUR DEVICE FILES FIRST !!!!
What is this
gmapsupp.img.part file????
If you download these 2 files
HEREUnrar it first and then copy "City Navigator North America NT 2011.10.gmap"
(in XP - C:\Documents and Settings\All Users\Application Data\GARMIN\Maps)
(in Vista, Windows 7 - C:\ProgramData\GARMIN\maps)
Then use mapsource and you see map