Notes about the M7A file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The M7A file type is primarily associated with 'Mapking' by Matlas Technologies, Inc. MapKing is a pan-region multilingual mobile mapping system in Asia. MapKing offers maps in English, Traditional Chinese, and Simplified Chinese. There is some discussion that would indicate you can rename Garmin G10 file to M7A for Mapking so it's possible you may be able to rename M7A to G10 for loading into a Garmin GPS device. If you can confirm this please drop FILExt a note indicating success or failure.