to patch it if you like to send our .img to any drive (not only nuvi, for example to :C or else) Just replace the original .exe with the patched one in MI folder, or use pietu's files.
I mean Mapinstall must be patched if you want to send the img to another drive and not to a nuvi directly.
If you don't patch MI you are allowed to send .img to nuvi only.
Patched file is here
[Only registered and activated users can see links. ]
Unlocking the img is another story , best tool to unlock an .img is [Only registered and activated users can see links. ]
Drag&drop the img in it and it will be unlocked; You can unlock the img directly in sd and nuvi, just drag the img.
(No unlocking method will work in some new devices and firmware: read gimgunlock0-03+mapsigpatch notes in its thread)