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The default behavior when set file association for a file type, in explore the extension won't show in file name again. Is there any way to let the file extension show again? In Windows XP this can be done by remove the file association entry, but it seems can't be done in Windows 7.

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In My Computer go to:
Organize -> Folder & Search Options
Click the View tab
Uncheck Hide Extensions For Known File Types
2'nd from bottom on image

alt text

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I thought EVERY SuperUser and Windows User knew this, but I must be wrong... – Mateen Ulhaq Dec 24 '10 at 18:51
Thanks for the reply. The thing is I want to hide file ext for known file types and ONLY display unknown types. My question is after registered an unknown file type, how to remove/delete/unregister it and revert it back to the status before registered. Sorry for not making it clear. – Stan Dec 28 '10 at 11:21

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