In addition to traxor's post:
Whilsts uninstalling make sure you exit your internetbrowser completely, also do a reboot before you install again (to make sure all traces are gone). Note that if you used an ad/spyware removal program you have to reinstall with sponsor because those programs criple the uninstaller. After that you can uninstall and reinstall as mentioned.
For more info see:
How to uninstall ad-ware/sponsor.