I fair bit of spyware sits as part of Internet Explorer to monitor websites you visit. This cannot happen unless IE is monitored, and the only way to do this is to make itself a 'plugin' to be part of it.
I would backup your computer before doing anything, and then let it work. Otherwise, you could use Lavasoft's Ad-Aware to check, safe that it will do a good job.
Either way, backup the computer before you do anything drastic or unknown.