I have some sort of virus that disables AIM and Internet Explorer and slows Firefox?

So, I have some sort of virus that has disabled me (on Internet Explorer) from using the address bar (when I type something out and press enter it gives me a message saying "The requested lookup key was not found in any active activation context") and I can't even type anything onto my homepage (Google). The same typing problem comes up when I try to message someone on AIM but not MSN. Also, Firefox has gotten very slow, often becoming nonresponsive for a minute or two and when I try to delete certain files it says "Cannot delete -file name-: Access is denied. Make sure the disk is not full or write-protected and that the file is not currently in use." My question is, is there anything I can do aside from reformatting? I ran Ad-Aware, AVG 8 and Avast (which my friend recommended) and while they have found problematic files, I can't do anything with them. Any help would be greatly appreciated, thanks.