Comment: There are several possible causes for this.
Solution: Microsoft provides the Inbox Repair Tool for correcting most problems with damaged Personal Folders (.pst) files. If you do not see the Inbox Repair Tool on the Start menu, under Programs > Accessories > System Tools, use Start > Find or Start > Search (depending on your operating system) to search your system for Scanpst.exe, since you will need to know the location of the .pst file that you want to repair.
When you run Scanpst.exe, it performs a number of tests. If it finds errors, it asks whether you want to make a backup copy of the original file. Always say Yes. It then tries to correct the errors. If you run Scanpst.exe against a .pst file that Outlook 2003 created for a local copy of Windows SharePoint Services events and contacts lists, you will get an error message that you can ignore. If you do receive the error message, see http://support.microsoft.com/?kbid=817966
For seriously corrupted PST files, try running Scandisk.exe under Programs > Accessories > System Tools first. Then Scanpst.exe, repeating 3 to 4 times until neither program returns an error. This technique has been known to restore data that the user thought was lost forever. If that doesn’t do it, try the following:
1. Outlook has no inbuilt way to reduce a PST or OST file that has gone over the limit. However, Microsoft provides a tool, PST2GB, which you can download to restore the file to operability. Note, however, that the utility truncates the data from between 25 and 50 MB, and the truncated data is not recoverable. The remaining data under 2 GB should be restored. The file “PST2GB” is available from www.microsoft.com (do a search for that term).
If you want to attempt repairs yourself, use a tool called a hex editor to edit the data in the file directly. Every Windows shareware site has a selection of hex editors. A recommended, free hex editor is the iHex editor (http://www.memecode.com/ihex.php), which loads only 64 KB of the file at a time, making it ideal for tinkering with extremelylarge PST files.
2. Make a backup of your PST or OST, then open the original file with the hex editor. You’ll want to remove a few characters from the middle of the file, then save it and try to run the Inbox Repair Tool (Scanpst.exe) to repair the damage you did with the hex editor. If Scanpst can repair the file, you should be able to open it Outlook again. If not, try removing some additional characters from the file.
If this process works, you could end up losing only one or two items. You may be able to recover all the data by repeating the process with a new copy of the file.