doubleclick and valueclick are cookies. you're just getting new ones each time you surf. it's normal. if you set your browser to reject all cookies you won't get them but then you may have a more difficult time navigating and staying signed in at some sites - even sites that don't attach 3rd party cookies including nu for instance.
you can sometimes opt out of 3rd party cookies. go
here for more info but you don't need ad-aware to get rid of them. if you set your browser to delete all cookies at log out you'll get rid of them automatically and this way continue to surf normally. go to file | preferences | privacy in opera and check "throw away new cookies on exit."
- js.