Product keys are no longer being accepted for renewals. You will have to create a new account in order to be able to use the product key. To use your product key uninstall One Care and install the One Care trial -
http://onecare.live.com/standard/en-us/install/install.htm To activate open One Care, select "Subscribe" and when asked for a Live ID create a new Live ID or use an existing Live ID that was not associated with your previous One Care subscription. Follow the prompts to set up a new account and you will be offered the option of using a product key as a method of payment.
Jim - MVP Windows Live - Forum Moderator - Live One Care - Live Mesh - Microsoft Security Essentials