Tried everything to uninstall One Care and nothing works, even when you use the Microsoft uninstaller it doesn't work.
After doing everything and then trying to reinstall it fails.
If you still cannot uninstall it corectly then there is a powerfull unistalling program called revo uninstaller its free. It force uninstalls by simply removing all files added by the program.
http://www.download.com/Revo-Uninstaller/3000-2096_4-10687648.html?tag=mncol&cdlPid=10892747
It does registry and harddrive removals.
** just stating my opinion not advertising it