When I do a google search in IE8 all links are redirected to adsense.previewmediastation.com.
My antivirus software (Norton) is not picking anything up. How do I get rid of this?
You probably have a BHO (Browser Helper Object) that is being evil. Go to Tools, Manage Addons in IE and disable everything.
Also, look for suspicious entries in shexview and autoruns.