WhenU and Fastclick both bring popup ads but both are easily defeated and
leave nothing behind when you remove them.

To remove the WhenU adware use the uninstaller in the C:\Program Files\Save
or C:\Program Files\VVSN folders. To disable the Fastclick popup go to the
Security tab of the Internet Options control panel and add www.bearshare.com
and home.bearshare.com to the Restricted Sites Zone.