Turns out that if you install Adobe Edge Code that the software claims to own every file on your system without an extension. That’s quite a claim, and also turns out to be something virtually un-Google-able to undo (give it a go!).

I managed to untangle it by looking at filetype associations in the Windows Control Panel:

…and observing that this means it has an extension of “.” – with no extension text on the end.

Then a trip to RegEdit (run ‘regedit.exe’ from the Start menu – you can do this on Windows 8 just by typing the whole thing; it won’t part-match the text and show possible completions) allows the following keys to be deleted:

[HKEY_CLASSES_ROOT\.]

PerceivedType”=”text”

[HKEY_CLASSES_ROOT\.\OpenWithProgids]

“EdgeCode.File”=”"

…and then finally Windows stops showing every extension-less file as belonging to Adobe!

A bit bizarre that every filetype-less file can be claimed, and that Adobe decides to claim them…