Whenever the computer is shut down incorrectly as in a power failure or when it hangs and you just have to force a shutdown, Outlook data files that are open for access may become damaged.  This may manifest itself in a variety of ways but frequently as a "MAPI" error or "record not found".  The first line of defense is to run a program called SCANPST.EXE.  This file is located on the C drive under Program Files.  Find the following Subdirectory: 
                     C:\Program Files\Common Files\System\MSMAPI\1033
and look for Scanpst.exe.  Double click on it to start the program.  It will ask you where the pst file is that you want to check.  If you haven't moved your Outlook.pst file, it will be found in the following subdirectory:
                     C:\Documents and Settings\Your User Name\Application Data\Microsoft\Outlook
Navigate to the Outlook.pst file and select it.  If any errors are found the program will create a backup called Outlook.bak and then make the copies.  If you already have an Outlook.bak, you may want to name the backup file differently, just in case.

2007.02.26  Changing the location of your "Outlook.pst" file

For some reason, Microsoft elected to bury the primary Outlook data file in a directory that is not usually accessed.  They may have done that to keep people from messing it up but it also makes it more difficult to locate.  In fact, the majority of Outlook users have no idea where it is.  That means they don't back it up regularly.  If you put the file in a directory under "My Documents", not only will you know where you put it, but when you create a backup of "My Documents" you also backup your precious Outlook contact information.

Here's what you have to do to move the primary OUTLOOK.PST file to another location.  First you must exit OUTLOOK.  Give it a few minutes to close all its files and fully exit.  Then navigate to the default directory where OUTLOOK.PST is located:

C:\Documents and Settings\Your User Name\Application Data\Microsoft\Outlook

Locate the file using Windows Explorer, cut it and paste it in the new location of your choice.  I also suggest that before or after you move it that you create a zipped copy of it for safe keeping.  You may want to append the date the the name such as "Outlook 2007-02-26.zip".  The zipped file will be very compact.  Making periodic zipped copies is a great strategy for protecting your precious information.

Once you have moved the file and before you open Outlook, you must go to the Control Panel, select Mail then click on Data Files.  REMOVE the Personal Folders reference then ADD the new personal folders reference by navigating to the new location of Outlook.pst.  Close the window and exit the Mail window.  When you restart Outlook, it will use the Outlook.pst found in the new location.