COMPLETELY unassociating extensions from default Open With programs

Brink said:

To unassociate the .pkg file extension, you would actually be deleting the .pkg key on the left side at those 3 registry locations below.

If you wanted to unassociate a different file extension, then you would substitute .pkg in the locations below with the other file extension instead to delete. :)

Code:

[-HKEY_CLASSES_ROOT\.pkg]

[-HKEY_CLASSES_ROOT\SystemFileAssociations\.pkg]

[-HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.pkg]

I have read about deleting those keys, but they say that it will completely wipe the .pkg extension from your device (any .pkg file). Is that true?

Brink said:

It will unassociate .pkg files so that they will no longer have a default program assigned to open them with.

Well, ok, I'll try to delete the .fsb keys in these 3 locations.
Could you explain how I make a backup of these keys, just in case if anything goes wrong?

Sorry for my late answer, I was very busy at my Summer student's work.
So, I'm trying to backup/export the 3 .fsb keys you gave as example to me, before deleting them.

[-HKEY_CLASSES_ROOT\.fsb]
[-HKEY_CLASSES_ROOT\SystemFileAssociations\.fsb]
[-HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.fsb]

However, I cannot find the second key [-HKEY_CLASSES_ROOT\SystemFileAssociations\.fsb]
(Nor can I find the .pkg inside SystemFileAssociations, but that is because it has already been restored to default maybe?)

What should I do if it isn't present? Just ignore it and continue deleting the 2 other keys?

Ok deleting the .fsb keys worked. The .fsb extension is now completely unbound. Thank you for all your assistance during this topic, Brink.
Does taking this action require any system restart?