The other day on my mac I moved my home directory from one HD to another (to separate my data from my system and apps).  I stupidly forgot that this would affect my Outlook.  After a bit of searching I discovered that the best way to get my outlook back was to copy across the old database file into its new location and rebuild it.  I did this and it didn't work and overwrote the old database file with a new one.

However all was not lost as I back up my files and so I restored my backup from the previous day.  When I create a new database file it has a little icon and when I open it in info it tells me that it's kind is a Microsoft Outlook Database.  But the restored file I have downloaded simply says the kind is "file" and there is no icon.

When in open Outlook and try and rebuild this database it fails. Can anyone suggest what I need to do to return this file back to a database file?  Is this a common problem with backups?