If you activated with the same LiveID used for your original subscription, it inherits the expiration from that. Check your subscription status at http://billing.microsoft.com and use the renew link to renew the subscription. Select the option to renew with a PIN or Token, which is the retail key from inside your new copy.
If you activated with a different LiveID and the Billing site and your PC don't agree on the actual expiration date, please contact support.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve