Hello sknatza, if you haven't already done so uninstall One Care from Control Panel>Programs and Features>Uninstall a Program. Download the One Care install cleanup tool and save it to your desktop - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=828910&SiteID=2
Right click the cleanup tool and select "Run as Administrator". When the cleanup completes download and install the One Care trial - http://onecare.live.com/standard/en-us/default.htm
After installation open One Care and select "Subscribe". When asked for a Live ID, enter the Live ID and password used originally to activate One Care. Your subscription status will be recognized and One Care will activate.