There is only one file type that uses the .MINESWEEPERSAVE-MS extension:
Minesweeper Saved Game
Saved game file created by Minesweeper, a classic puzzle game included with Microsoft Windows; stores the state of the minesweeper map, including revealed blocks, flagged blocks, and the elapsed time; used for restoring the last opened game state when the program was closed.
You cannot save Minesweeper saved games from within Minesweeper program menu. Instead, when closing the program, it asks if the user would like to save the current state. If the user chooses to save the state, the game resumes the next time the program is opened.
In Windows 7, MINESWEEPER-MS files are saved by default to the following directory: [user]\Saved Games\Microsoft Games\Minesweeper\.
Updated: June 29, 2011