It sounds rather like a trojan has taken over the internet explorer browser. The virus "key" will be placed in the registry which effectively redirects your internet explorer to do something different. Can I suggest you run AVG 8 free version and/or PCtools Spyware Doctor free version, available from the Google free site. I use both and they always find tracking cookies and adware to get rid of. they are very good at finding Trojans too!
Chrisf989
August 2008