http://www.perfectnav.com/

PerfectNav is a 'Add' add-on for Kazaa. It might also be installed by other applications. I was having problems with it too.

If you're using Kazaa, and this was how you were 'infected' by PerfectNav, you can get rid of it by unistalling Kazaa. A less drastic remedy is to use another program called 'DietK' to remove or disable PerectNav and other ads. DietK also has other features to help Kazaa users. DietK is free, and you can get it at: http://www.dietk.com/

Alternatively, the following page has instructions for editing your registry and files to manually remove PerfectNav:

http://www.kephyr.com/spywarescanner/library/perfectnav/index.phtml