Unknown file extensions appear as type file.ext"

[jasonb]

For a couple of months now, I'd been experiencing a really annoying problem which is slighly hard to describe in general terms but which I can relay by way of an example.

Let's say I double-clicked on filename.extension - and this is an extension that I don't yet have associated with anything. I'd get the following familiar file association dialog:

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Windows cannot open this file:

File:    filename.extension"

But note that, for some inexplicable reason, it added a " to the end of the extension name. This caused me problems getting some types of media files to play with the appropriate player, because, if I looked in my registry, I'd get both extension and extension" listed - and (for the filetypes I've had problems with somewhat recently - although I'd since just let it go) Windows would invariable use the wrong player. When deleting both entries, it would keep coming up with extension" when trying to associate a new one.

I couldn't for the life of me figure out what had been corrupted such that it insisted on seeing all extensions with a quote at the end of them.

I ended up fixing this by the simple expedient of exporting the HKEY_CLASSES_ROOT\Unknown key (and all of its subkeys) from my work XP machine, then importing it into my home computer. Voila! No more strange " at the end of all of my extensions.

I wasn't 'inquisitive" enough to actually compare the two and see what was causing the difference. However, for anybody who may experience this problem in the future, here is what the "good" registry code looks like (you can save this to a .reg file and import it yourself):

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REGEDIT4

[HKEY_CLASSES_ROOT\Unknown]
"AlwaysShowExt"=""
"QueryClassStore"=""

[HKEY_CLASSES_ROOT\Unknown\shell]
@="openas"

[HKEY_CLASSES_ROOT\Unknown\shell\openas]

[HKEY_CLASSES_ROOT\Unknown\shell\openas\command]
@=hex(2):25,53,79,73,74,65,6d,52,6f,6f,74,25,5c,73,79,73,74,65,6d,33,32,5c,72,\
  75,6e,64,6c,6c,33,32,2e,65,78,65,20,25,53,79,73,74,65,6d,52,6f,6f,74,25,5c,\
  73,79,73,74,65,6d,33,32,5c,73,68,65,6c,6c,33,32,2e,64,6c,6c,2c,4f,70,65,6e,\
  41,73,5f,52,75,6e,44,4c,4c,20,25,31,00