Got these via Google may be worth looking at.
First try the repair tool, scanpst.exe, on your default pst.
Search, to include hidden if you cannot find it.
If you used the OL backup addin, the backup is actually only a copy of the
pst, by default named 'Outlook Backup.pst' To restore this pst it is only
neccessary to open it, within OL. You might wish to rename it prior to
opening it. If moving any pst's do not overwrite any existing pst's
Run the Inbox Repair Tool
1. Click Start and point to Find, or Search, depending upon your operating system.
2. In the Search for files or folders named box, type scanpst.exe.
3. Type the path and file name of the pst file, or click Browse to locate the file using the windows file system.
4. Click Start.
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What the Inbox Repair Tool Does
When you run the Inbox Repair Tool on a Personal Folders (.pst) file, it does the following: • The Inbox Repair Tool analyses the Personal Folders (.pst) file directory structure and item headers to try and recover all folders and items.
• If the Inbox Repair Tool recovers the Personal Folders (.pst) file, it means that the repair tool found problems, and repaired what it could.
• The Inbox Repair Tool tries to turn any file into a Personal Folders (.pst) file. (For example, if you rename an executable file to "Something.pst," (without quotation marks) the tool changes the file to a mountable .pst file).