Go into Control Panel then Mail
click E-Mail Accounts button
Select View or change existing.... then hit next
Somewhere near the bottom should be a New Outlook Data File button, click it
Select Office Outlook Personal Folders File (.pst) then hit Ok
Type a filename for the pst then hit ok
Another window will pop up asking about encryption and passwords blah blah, type a name in the box at the top (e.g Personal Folder2) then click ok. You should now be back to the window with the New Outlook Data File button on it.
From the dropdown box next to the New Outlook Data File button select your new Personal Folder (Personal Folder2) then click finish.
You should be able to open Outlook now but you won't have any of your old emails.
What you can then try is importing your old mail from the original pst.....
In Outlook click File then Import and Export
Select Import from another program or file then hit next
Select Personal Folder File (.pst) then hit next
Click Browse and find the .pst file the error message was talking about, click Ok then Click Next
Assuming Outlook can read that .pst (it may not given the error before) you should get a list of your old folders, select Personal Folder at the top and make sure Include subfolders is ticked. Underneath select Inport items into the same folder in: then chose your new personal folder file (Personal Folders2).
cross fingers then click finish.
James