This is quite an easy one for me. I like challenges.

1 - Unlock using Fast IMG Unlocker or similar. My copy still has locked images.
2 - Open the .img file with GMapTool
3 - In GMapTool > Write > Set Transparency = transparent > Write All
4 - Copy the new US_GarminLakes_Full.img to the \Garmin folder on a USB thumb drive.
5 - Open Garmin HomePort - The mapset now appears as "Garmin Lakes g2"

Have fun.