I just found your post in the OFF TOPIC folder and have moved it to the General topic folder.
How can the account not exist if you claim to receive emails at it? I suspect that you are not using the correct LiveID for your subscription. Open OneCare, click on Help/About and you will see your subscription ID. This is the LiveID for your subscription. Sign in at http://billing.microsoft.com with that LiveID and change your credit card details.
Alternatively, when the subscription expires, simply reinstall OneCare and purchase a new subscription by activating within 15 days of the reinstall with a different LiveID and your payment information.
You can also contact support for help. Note that this forum is for customers helping customers.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve