Normally if you try to access a website which is not existed, IE will go to the html said something like website is not existed, check connection and DNS error(can't remember, sorry). I know that html file is located something in the windows folder. Now whenever I go to a website which is existed. It will go to http://www.internetoptimizer.com. How do I change it back? Thank you.

U may try to scan your pc with adaware or spyware software, where that might help u to clean out some annoying programs staying in your pc.