Where does Windows store its “Open With” settings?

Question

I\'m trying to programmatically check file associations by the file extension (for example .jnlp files). I keep reading that

Answer 1

This is a two-part look-up.

First, you look up the default value of HKEY_CLASSES_ROOT\[file_extension]. For your extensions, .jnlp, the value is "JNLPFile". Let's call this the [file_descriptor].

Now you can look up the default value of HKEY_CLASSES_ROOT\[file_descriptor]\Shell\[action]\command (where [action] is the shell action you are interested in, e.g.: Open, Print, Edit, etc.).

Answer 2

On:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.jnlp\OpenWithList

Tip: Edit>Find is pretty handy at these situations. :)

Answer 3

Take a look in:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\

and the sub-key of that is the extension you reassigned. Under that there will be the UserChoice and OpenWithList sub-keys which will contain your redefinition.

You may also want to read http://support.microsoft.com/kb/950505 which talks about your issue.