clean install

If you like IE7, reinstall it and see what happens.

Actually, using FireFox is a big plus as far as security and malware prevention is concerned

I happen to be one of the 400 million or so who are using Internet Explorer safely who happens to disagree with that statement. I will concede the FF, on its own, is safer out of the box, but just because you decide to use IE7 that does not mean you will be unsafe or compromised. Nor does it mean if you use FF or an alternative browser you will be safe. It just is not true.

Regardless the browser of choice, whether IE7, FF or whatever, you still must practice safe computing and keep your systems:

Patched to the latest version (that means SP2, and IE7, not IE6),
Updated with critical updates,
Blocked behind a properly configured firewall and spam blocker
Scanned with updated AV and AS program.

And finally, you never open attachments or downloads with first scanning, you don't click on "click here to stop getting these emails", and you need to stay away from sites badguys are known to wallow in, such as porn, P2P, and others.