Before going the reinstall route, try resetting your backup plan:
http://social.microsoft.com/Forums/en-US/onecarebackupandrestore/thread/5f18a60d-add4-4ff2-87cf-021db7e81917If your older computer was a Hub in a OneCare Circle and you configured Centralized Backup, you may need to make this one a Hub, too, in order to configure backup or to reset the backup plan.
-steve
Microsoft MVP Windows Live / Windows Live OneCare, Live Mesh, & MS Security Essentials Forums Moderator