It's most likely CWS. Get CWShredder here:
http://www.majorgeeks.com/download4086.html
And if you *must* use IE, visit this page:
http://sivran.netfirms.com/IE.html
Follow the instructions, get TrustSetter, SpywareBLaster, Spywareguard, and ScriptSentry from the links provided. It's all free, and your IE browsing will be safer for it.
As others have said, and as
CERT and the
US Government have strongly suggested, you should switch to an alternative browser.
Edit: If CWShredder fails to clean it up (and if it is CWS, even CWShredder might fail. Some variants of CWS are
very nasty), visit
http://www.dslreports.com/faq/8428 - If you've followed those steps, and still you have problems, make a post here:
http://www.dslreports.com/forum/security and someone will help you.
[ July 04, 2004, 18:41: Message edited by: Sivran ]