Strange that avast didn't do anthing about it.
Welcome to Sevenforums, by the way!
Update both it and malwarebytes and do a full scan on both, one after the other. Then go running, or have a hearty breakfast, etc. (it may be a while).
Then go into "manage add-ons" in IE and make sure you only have add-ons you need, such as shockwave player. disable any other ones that you don't. I've seen many "coupon" add-ons in the past and truth is they aren't needed and often pose a security risk. *Important! Make sure all important windows updates are installed, as many of them are security fixes!
You might also consider installing many of the optional windows updates that have to do with IE, and if you don't already, IE9 is more secure than IE8 and worth the upgrade!