From MozillaZine Knowledge Base

kenbo11 08 Feb 2008 reports that "C:\Program Files\Internet Explorer\ieproxy.dll needs to be removed or renamed. Otherwise the key you just deleted will come back and the problem will still exist.". See http://forums.mozillazine.org/viewtopic.php?t=626896 and my reply. Alice 04:02, 9 February 2008 (UTC)

Warning added

This article is dangerous. I added a bold warning. See the following Firefox Support forum posts. Alice 01:34, 17 February 2008 (UTC)

Firefox takes over when I try to open a website with Internet Explorer

I accidentally deleted an entire directory of keys instead of just one.