There is a simpler way round this and download Garmin homeport!
I have the same plotter take a copy of the maps and your tracks, weypoints, routes from the plotter onto the SD card, then put the SD card into your pc open Homeport and all your plotter info and maps will be on your PC you can then delete and clear up all of the above and use it for planning by making routes on the PC and copy back to the SD card and update your plotter. Homeport cost £29.