If you’ve ever seen a .menc file before, you probably saw it on an external memory card that you pulled out of your Windows Phone device. Â
Essentially, .menc (Mobile Encryption) files are just your personal data (the PIM.VOL file that contains all of your Contacts for example) that are encrypted. The extension of .menc lets the Operating System (OS) know which files are encrypted, and whether or not they can be opened by the user.  To do so, the previously recorded key (user password) must match the key provided by the user when unlocking the device. But you won’t see those .menc files, because they are typically hidden by the OS so as not to be visible to the end-user during casual browsing.  If you ever chose to encrypt the files you store on your external storage (external memory card, etc), then they may be visible if you took that card to another computer or device for viewing.
If you’re trying to recover those files, then you have to meet some rather special requirements in order to proceed. Unfortunately, if you have Hard Reset the device, or have a different device than the one that the files were originally created on, then the encryption/decryption keys are now lost or no longer the same, then sadly your files are totally inaccessible.Â
However, if you have access to the same device that the .menc files were originally created on, and you have NOT performed a Hard Reset on the device, then you can still salvage the files:
- Turn the storage card encryption off: Go to Start > Settings > System > Encryption (varies by your Operating System version) and uncheck the “Encrypt files when placed on a storage card†box. From this point forward, all NEW files created on that card will be unencrypted, but existing files will still be encrypted.
- Next, bring-up your favorite File Explorer, then browse to your Storage Card. Make a new folder on the storage card, and call it “OLDDataâ€. This folder will, of course, be unencrypted.
- Now, find whatever files you want to decrypt and copy them into this folder. Those files will be decypted as they copy into the new folder. You can now read these files on any other computer or phone.
Congratulations, you’ve just saved some data.  Hopefully it will turn out to be highly important data, which will make your victory taste just a little bit sweeter…