IE Help Necessary

I clear my history and auto-completes just about every session. I cleared them this morning. This afternoon, I opened my history window, and in the history was an advertisement for warez sites, and window after window after window opened up, prompting me to approve applets, view pages, and download files. Google was still set to my home page. I cntrl-alt-deleted the program and rebooted. As soon as I started up IE again, the windows opened automatically. I rebooted and went into the Control Panel, where I cleared the disk cache, auto-completes, and history. I confirmed that Google was my home page and set the browsing level to “highest security.” Everything seems to be working okay now.

Can anyone tell me how the hell an advertisement/banner/web site appeared in my history window? How did this happen? I just scanned for viruses with new definitions; none were present. I don’t approve those little applets if they ever appear (except for Flash or Microsoft, etc.) Can anyone venture a guess as to what happened?

I guess I’m also asking this:

All I’ve visited today is site and CNN, and I had no problems this morning, so how did it just happen now?