help - IE was hijacked

Hello, I need some help. Since 2 days there appears a popup-window with always the same banner (it is some xxx-banner) althouhg I am not browsing some "related" sites. It happens unregularly, sometimes when I am going to [login to view URL], somtimes when I change to [login to view URL] etc. always this new popup-window opens with that porno-banner. How can this be??? And how can I remove it? It must be something which was installed on my system, but I have no idea where it could be! I used Lavasoft Ad-aware 6 for removing all the junk from my system, restarted etc. but still this popup window will open while I am surfing with Internet Explorer (Version 6). Also I checked my registry for the "run" key if there is no "new" software which automatically starts during boot-up, but nothing suspicious there... How can I find and remove that stuff that makes this popup window open? ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Complete ownership and distribution copyrights to all work purchased. ## Platform MS Internet Explorer 6 on Windows XP Home