Two things:

1: Internet Explorer is unsafe to use in any sort of regular way, so you're probably better off with it not working

2: Since it sounds like you must have IE6, you probably picked up a bunch of malware and that's causing your performance issues

So, first, why not tell us what you do about malware, and then second, be sure to pick one of the following to be your new full time browser, leaving IE for rare occasions when there's no other choice. Firefox, Seamonkey, Flock, Opera, Safari. Doesn't matter which one you pick, just pick one and treat IE like the diseased leper it is.