[SergioK]

The 2820 will go into two different modes when you connect it to your PC. It will go into either Garmin mode or USB Mass Storage mode. In Garmin mode, the unit will interface with the Mapsource program to xfer routes, waypoints, etc. In USB Mass Storage mode, it works just like any other USB storage device so that portion will show up as another drive. You can then drag and drop your MP3s into it. IIRC it has about 700mb of space.