I've moved your post from the Off Topic folder where you posted (You apparently missed this at the top of that folder -DO NOT POST HERE! Folder used by moderators to move off topic ite...) to the General topic folder.
Open OneCare, click Help/About. It will list the subscription LiveID that you need to sign in with.
If you need to reset the password, http://account.live.com
If that doesn't work, you can contact support as a "trial" user via email per the instructions here:
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
Alternatively, the unofficial path - send me an email at sboots@mvps.org with a subject line including "OneCare" (to get past my spam filtering) and in the message body, tell me what country you are in, your forum nickname, and paste this link:
http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=4197181&SiteID=2
I am not online 24x7, so you may be waiting for a reply, but I'll do my best to hook you up with support.
-steve