Hi, Geoffrey.
Did you call support already? They can tell you the LiveID that belongs to your product key.
I deleted it from your post as this is a public forum. Although the key cannot be technically used by anyone else since it was used to activate your original subscription, it is still not good to post a key to a public location.
If you don't recall the LiveID you used for your subscription, you will need to contact support who can provide that information to you using your Key and/or contact information.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
Alternatively, sign in at http://billing.microsoft.com with email addresses that you have set up as LiveIDs and one will show your subscription listed - that would the LiveID to use to activate with.
If you are not being helped by support, please let us know the case ID.
At this point, you can reinstall OneCare from http://onecare.live.com (after uninstalling it first) and you should have 15 days until it needs to be activated.
-steve
