Question
Can a computer's backup archive be moved to a new or different user?
Answer
No, you can’t move archives from one user to another user. You can, however, change the email address of an existing user as long as that new email address isn’t already associated with a CrashPlan account.
To move a computer to a different user without its existing backup, assign your computer a new ID. The new user will be able to start a backup of their own for the device.