Hi Roz,
I use a free program called AD-Aware ( link below ) that I run every second day to get rid of Tracking Cookies and Data Miners. These are the terms that are used by the software and not too sure of thier status. I find that by utilizing this software it does keep down the spammers and unwanted emails to a minimum.
There are a number of other free software programs available and I also run a Spy-Doctor to do a similar job as Ad-aware.
Steve will probably help you more with this as I know how annoying the unwanted emails are.
here's the link. just click on the free download of follow the instructions,, fairly easy .
http://www.lavasoftusa.com/
Cheers Phill