I've moved your post to the Tune-up topic folder as this is the part of OneCare that monitors the status of Automatic Updates.
Go to Control Panel and click on Automatic Updates (this is from the Windows Start Menu). Enable AU from there, selecting either to download and install immediately or at a scheduled time (default is 3:00 AM daily).
If your PC is part or a corporate Active Directory Domain, meaning it is a company PC in a corporate environment, it may have Automatic Updates disabled. If that is the case, there isn't anything you can do to enable AU and OneCare will always be at risk. I suspect that this is not the case for you, so if the Control Panel path does not work, please contact support for help:
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve