Internet Explorer problem.

I have got a problm recently. When ever I open a internet explorer it automatically opens a search web site having diffrent name e.g. search group , netsearch etc. but having same ip address 81.211.105.9 Even if i reset home page and delete all history and temp. files through property dialog box of IE , this site again opens automaticaly.

How to solve this problm. I have checked all entries in HOST file but not a single entry there for this site.

Any solution ?