Set IE as default... (WME)

[BirchHill]

I loaded Mozilla Firebird as an additional browser which became my default browser (instead of IE 6). I've checked the setting for IE in Tools-Internet Options-"Internet Explorer should check to see whether it is the default browser"; however, it still does not prompt me or ask the question if you want IE to be the default browser. If appears the Mozilla Firebird prevents IE from even asking the question. I've shut down IE as well as rebooted without success. Is there some registry tweak that will let me again assert IE 6 as the default browser, without deleting Firebird?