How to delete a file association? [duplicate]

Open an elevated command prompt with administrator privileges.

Remove the file extension association from its assigned file. Type in the following command and press Enter:

assoc .ext=

Replace .ext with the extension name that needs to be disassociated. For example, to disassociate WinRAR's .rar extension, simply type: assoc .rar =

Note that after disassociation of a file extension from file type, the default program for the file type will no longer be shown in the "Open With" list for the file extension.

Clear and delete the default program used for the Open command when launching files of this type. Enter the following command and press Enter:

ftype FileType=

Replace "FileType" with the actual name for the file type associated to the file extension to be removed from the system. For example, for WinRAR, type ftype WinRAR=

Note that if you don't know the correct "FileType", simply type assoc (associated file type will be shown after the extension) or ftype to get a listing of all file types defined in the system.