Insert the USB key into the computer you wish to restore the files to. Open One Care and reset your backup plan to use the USB key as a backup destination. How to reset a backup plan -
http://social.microsoft.com/Forums/en-US/onecarebackupandrestore/thread/5f18a60d-add4-4ff2-87cf-021db7e81917 Assuming you have limited free space on your USB key perform a custiom backup and back up a single file. When backup completes perform a custom restore and select ""Restore files from another PC" and select the folder you created as the restore destination.
Jim - MVP Windows Live - Forum Moderator - Live One Care - Live Mesh - Microsoft Security Essentials