I'm going to move this post to the ant-virus folder because of the subject line, but to add to Jim's answer, when you install OneCare, it does not use the product key. Upon completion of installation, it is in trial mode, fully functioning. You will have a link to subscribe or activate, which then allows you to purchase online or input the product key after you have signed in with a LiveID. That LiveID is your "key" from that point forward for all things to do with your subscription and will be needed to reinstall, activate on a 2nd or 3rd PC, renew, and contact support.
If OneCare indicates that your status is at risk, you need to open OneCare and it will tell you why you are risk. It may be as simple as needing to configure and perform a backup or it may be that a conflicting program was detected that must be removed. It can also mean that it is unable to reach the back end servers to update signatures.
-steve
