How to open a .mny file
Start here. Microsoft’s own free Money Plus Sunset edition still opens .mny files with no activation — use it if you only want to look. This guide walks that route, then explains the four places it stops being enough.
How to convert a .mny file to CSV
Renaming it does nothing and no spreadsheet will import one. Why that is, what the free route can manage, and exactly which fields land in the CSV — including the ones that do not.
When a .mny file will not open
Four quite different faults look identical from the outside: normal encryption, a password, an unsupported version, or real damage. How to tell which you have before trying fixes on your only copy.
Moving your Money data into Quicken or GnuCash
Neither can read a .mny file directly. The two-step route that works, which interchange format to choose for which program, and an honest list of what survives the move.
What to use instead of Microsoft Money
Paid desktop, free and open-source, or simply a spreadsheet — where people actually move to, and why getting the history across is the part that blocks them, not the choosing.