Sorry but you're not providing enough information.

What exactly have you done?

You say you "loaded a backup". HOW? You also say you installed multiboot. HOW and WHEN? (i.e. before or after "loading the backup").

Plus, if you're N900 can charge then it can also connect to a PC. Which OS are you using?

Plus, the folders you mentioned above (pre-backup.d, etc.) are just the settings for the osso-backup program, which are useless for restoring, especially if you are not using the osso-backup program to restore the backup.