Thankfully Microsoft has included utility called Inbox Repair Tool / scanpst.exe located in your Microsoft Office installation sub-folder. Exact scanpst.exe location will depend on your installed Microsoft Office version as well as actual Microsoft Office installation directory path chosen during initial setup.
In our example we repair Outlook 2007 installed on Microsoft Windows XP Home Edition computer. If you are unsure about your Microsoft Outlook or Microsoft Office version it may be simpler to use your operating system search function to search for file named scanpst.exe directly (when using Microsoft Windows search feature make sure to enable search hidden files and folders as this file may be hidden by operating system defaults).
As you can see our repair tool resides under C:\Program Files\Microsoft Office\Office12 sub-folder...
If we had Outlook 2003 our last sub-folder would be Office11, for Outlook 2002 Office10, etc.
Double-click to open it either form the search window, or by browsing to it's physical location on the hard drive.
Now you will need to browse to a location of your Personal Folder File. There are a few different ways to find out your Outlook PST file location, but the best bet is to open your Mail icon under Control Panel...
You should see dialog below... Click Data Files button to open list of your Personal Folder Files...
You will see a list of all your PST files along with their locations on your hard drive. Clicking on Settings or Open Folder buttons will also take you to dialogs where you can see physical location of your PST file (default name is usually Outlook.pst). If you can not copy file location electronically, please write it down on a piece of paper as you need it in the next step.
Lets switch back to our Inbox Repair Tool / Scanpst.exe window... Clcik Browse button and use newly opened explorer window to get to previously written down location of your PST file. Double-click or select and Open actual file (usually Outlook.pst).
Click Start button to begin... Inbox Repair Tool starts scanning your PST file. Depending on your computer speed, available system resources, and size of your PST file this process could take a while. Let it run!
You should see dialog below after scanning process has been completed... Keep in mind that your actual report information is going to be different... Review it and click Repair button when ready.
Inbox Repair Tool / Scanpst.exe begins actual backup and repair of your PST file... Again, be patient as this process could take a while!!! We have seen a repair process taking over two hours on some older machines with badly corrupted PST files. Do not interrupt this process even if your computer appears to be locked... Run it overnight if you have to.
Click Ok when repair process has been completed... Your Outlook should now be able to open providing it's original problem was a corruption of your Personal Folder / PST File. However, there is no guarantee...
Below is an official Microsoft support article on this subject you may find more useful than our amateur instruction: http://support.microsoft.com/kb/287497