If you happened to hit an issue with uninstalling Live OneCare, give this tool a shot:
This tool was developed to cleanup both OneCare v1.1 installations (older) as well as the current version, and the tool works on XP, Vista and Seven.
To use this tool, save it to your desktop. If running Vista/Seven, right click the saved file and select Run as Administrator. If using XP, simply double click the downloaded file to run it. You must be an administrator to run it.