If it doesn't appear in the Help/About screen in OneCare, this is likely an older install of OneCare. The early installs didn't show this pre-1.6, I believe (or maybe 1.5). Anyway, if you are trying to make it a hub, I assume you have other PCs running OneCare. Can you check Help/About on them?
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.
-steve