Can you let us know what the Zynga Toolbar error is telling you?
Also, Is the Zynga Toolbar entry in Start > Control Panel > Programs > Uninstal a Program area?
If you use Internet Explorer, select Tools > Manage Add-ons > Enable or disable add-ons. Is the Zynga Toolbar showing there?
Just need to know some particulars so we can figure out what strategy to use.