If you happen to own one of these, and to have acquired new maps that when loaded to the device claim that they're incompatible with your license, this is the way to unlock them. Don't forget to backup your files\maps before you overwrite them.
Disclaimer: I take no responsibility if this screws up your device\computer in any way, or if for some reason the GPS somehow makes you drive your Mercedes into a river. I didn't make these files, and I'm not hosting them. I'm not affiliated with Mio, any of the sites I've mentioned or the idiot that drove her car into a river.
So where were we? Ah -
1. Connect the device to your computer via USB. You should see two new mass storage drives - one for the device itself, and one for its SD card.
2. Update to the latest version from Mio through their "MioMap v3 Updater tool".
3. Go to this website, scroll down to the bottom and download the files.
4. Copy them to both the device and the SD card, overwriting the existing files
5. Copy your new maps (.fbl files) to the maps folder on the SD card
6. Reboot your device (by holding the power button and then choosing reboot)
7. Serve cold