try a spyware removal program like Ad-Aware and Spybot Search and Destroy
OR
New Trojan called Qhost Hijacks Your Web Browser
A new security threat emerged recently that can "hijack" Internet Explorer
and redirect the browser to the hacker's web site instead of the site to
which the user wants to go. If you find yourself ending up on the wrong site
when you type a URL (especially when you attempt to access popular search
engines such as Google or Yahoo), you might be a victim of this Trojan. It
works by changing Domain Name System (DNS) server settings. For more
information, see: http://www.winxpnews.com/rd/rd.cfm?id=031007SE-QHost
