Get rid of Address.com in IE

I’m running IE5.5sp2, and if I type an invalid URL in the address bar, instead of giving me the normal Microsoft message and/or error 404, it takes me to www.address.com/badadd.asp?url=xxx
with the “xxx” being the invalid URL, it also has an annoying pop-up add for address.com. I’ve already checked the “customize search settings”, and also cleaned address.com out of my registry, but it still happens. Also, in my taskbar, the button for IE changes to “Error 404-Microsoft Internet Explorer”. Help me get rid of this advertising scourge.