Ok i've done some research on the Navman MY series and it appears that they are a rebranded Mio Moov type device.
So download
[Please Register or Login to download file] which is the official Mio Moov unlock.
Follow the instructions on
[Please Register or Login to download file] webpage entitled
Installation Navman F10, F15, F25, S-Series, C-Series / Mio Moov-SeriesNow your device boots to a desktop and you can run any software you like. Tomtom and iGO Primo work best.
[color="red"]Please be aware that Mio Moovs can be bricked by incorrect editing of it's startup files, And as always you do this at your own risk![/color]