IE8 redirector not being detected

I use IE 8 on a Windows XP PRo computer.  My IE gets redirected constantly to shopping sites.  I ran scans with Norton, MalwareBytes, and Super AntiSpyware - they all come up clean.  I even scanned my external hard drive.  I don't notice anything suspicious in my add/remove programs list.  And I've checked the proxy settings in IE.

 

Any suggestions would be appreciated.