also recommend spyware blaster (once you've cleaned up your system). this is from the faq:
"#1) What does SpywareBlaster do?
-Unlike other programs, SpywareBlaster doesn't scan for and clean spyware. Instead, SpywareBlaster provides protection against spyware ever installing and can also prevent spyware from running if it is already installed on your machine! SpywareBlaster can also protect against spyware/tracking cookies (this cookie protection function requires Internet Explorer 6 or above - the spyware protection mechanism even works on Windows machines without Internet Explorer).
#2) How does SpywareBlaster's protection work?
-SpywareBlaster works by settings "kill bits" in the registry. These "kill bit" registry entries are set for the spyware ActiveX CLSIDs (unqiue IDs that identify an ActiveX control). When a kill bit is set for a CLSID, the ActiveX control that uses that CLSID cannot install itself via your browser, nor can it run if it already installed. Microsoft sometimes uses these kill bits for fixing Active-X security holes."
http://wilderssecurity.net/spywareblaster.html