Try running a scan by Ad-aware, you'll be surprised by the amount of dodgy cookies that you will have and were unaware you had, and thought you had deleted by emptying your temp. int. files
Pop-ups are particularly bad at this, trojans and all sorts in there...But dont listen to me, read it all here...
http://www.lavasoftusa.com/
and go to download. Takes nano seconds on broadband, cant speak for modems...