XdN File Association

This is a new tool for Windows Vista made to correct another issue with the OS… This one removes (incorrect) file extension associations.

Unlike previous versions of Windows … If you accidentally associate the wrong program to a certain file extension under Windows Vista, it does NOT let you remove that association (without opening up the Registry Editor, going to a certain key, deleting it, etc).
Vista will let you change the association from one program to something else, but not let you remove a program from the list.