OneCare renewals and purchase are no longer offered. You may get a free 6 month extension if your current subscription is about to expire.
See this post: http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/0000c782-ed1b-4ed3-8afb-87989bb9638c
Open OneCare and click Help and then About to see your Subscription ID. That is the LiveID to sign in with.
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://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
-steve
~ Microsoft MVP Windows Live ~ Windows Live OneCare| Live Mesh|MS Security Essentials Forums Moderator ~