Answer by e Thomas for How do you remove a default program association for file types in Windows 7?

I could not find the correct Windows Registry line, so I used a work around. On my desktop, I created a text file named "deleteable.txt". I changed the extension to .exe. Next, I used the control panel to change the default program assigned to the desired file extension to the new "deleteable.exe". I then closed the control panel, and finally deleted the desktop file.