OneCare backup can back up to any blank CD or DVD. I suggest using a name brand disc of write one discs - CD-R or DVD-R/+R. RW type discs tend to be a problem.
If you are unable to perform a backup, please contact support for help.
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