There is only one file type that uses the .MINISO extension:
Mini Image Destination File
Image file format used by DVDFab Blu-ray Copy, a program that enables users to copy Blu-ray content to a Blu-ray, DVD, and AVCHD disc; similar to an .ISO file but much smaller in size.
The MINISO format allows you to play Blu-ray folders and files. When you copy a Blu-ray disc or folder to a folder on your hard drive, the MINISO file is created. If you double-click the file it will be mounted and ready for use, however you must keep the source folder for the MINISO file on your hard disk.
Updated: August 14, 2015