Okay so Internet Explorer has started closing on me and I'm getting ad pop-ups any time I try and load it, so first off any advice on how to fix this would be great.

Anyway I'm trying to start using Firefox instead, as although it still seems to be letting in infections (which I keep seemingly getting rid of then return), it at least will open. I have it set as my default browser, but things like the inbox link from MSN Messenger, and Windows Update still try and open in IE, is it possible to change the settings so they open in Firefox?

Thanks a lot.