Umm. I forgot this . . . This is from early September:

“Invite your friends and family to signup for the Windows OneCare Beta!Do you know others who are interested in trying out Windows OneCare? We are now at the point where we would like to expand our > group of beta testers. We encourage you to extend Windows OneCare beta invitations to your friends and family. Just have them go to, sign in with their Microsoft® Passport Network credentials, type in OneCare (case sensitive) when prompted for the guest ID, and follow the instructions from there.”

you can also go to the OneCare website, and sign up there, should you wish.