You prolly didn't close your internetbrowser fully (from taskbar and systray also).
So now the steps are:
1. uninstall plus
2. reboot
3. reinstall plus! with sponsor
4. uninstall immediately (do not use ad/spyware removers in between and make sure you got your internetbrowser fully closed this time)
5. reboot
6. reinstall plus! without sponsor
done!
If you still got any searbar in your internetbrowser after that it can't be the one that comes with plus!
Post a screenshot if there still is one, it will help us figure out wich one it is
/ 
