If I understand you correctly, you didn't run out of room, but you're right on the edge? And you were trying to use TomTom Home to move the map?
If that's the case, you can hook up your TT and just copy the entire map folder from internal memory to the SD card using whatever normal file copy method your PC's OS uses (instead of Home), then delete it from the internal memory. Not knowing what device or map(s) you are running, all I can tell you is that the map folder will be in the root of your TomTom and should make some obvious reference to the countries (North America, Western Europe, etc.). To your PC, your TomTom looks like two external disk drives now that you have the SD card installed, so you'll have to look and identify both the internal and SD.
Before you do anything, we always recommend you make a full copy of your TomTom to your PC's hard drive, too. Now that your map will be on your SD card, you'll want to be backing that up to your PC's hard drive as well once you're done.
