Microsoft Outlook backs up data to personal storage folders, or .pst files, on your computer. E-mail messages, contact information, calendar appointments, tasks, notes and journal entries can all be backed up to .pst files. Unfortunately, if one of these .pst files becomes corrupted, you may experience problems starting or running Outlook. If you encounter an error message describing a problem with Outlook being unable to access a .pst file, try using hex editing software to view and edit---and hopefully repair---a .pst file without using Outlook.
Open an Internet browser to search for hex editing software to download and install. A hex editor will allow you to view and edit the Outlook .pst files once you locate them in Steps 3 and 4.
Download and install hex editing software compatible with your version of Windows.
Open a Windows Explorer window in Windows 7 or Vista by clicking on the Windows icon in the lower left corner of your screen and selecting "Computer." In Windows XP, click on the green "Start" menu in the lower left corner of your screen and select "My Computer."
Click on the Windows Explorer Address Bar to navigate to the Outlook directory. In Windows 7 and Vista, type: "C:\Users\username\AppData\Local\Microsoft\Outlook", where "username" is your Windows user account login. In Windows XP, type "C:\Documents and Settings\username\Local Settings\Application Data\Microsoft\Outlook", with "username" as your Windows user account login.
Make a backup copy of the original .pst file you will be editing by right-clicking on that .pst file icon and selecting "Copy" from the pop-up menu. Then right-click in a blank area anywhere else inside that same window and select "Paste."
Rename the original .pst file by right-clicking on its icon and selecting "Rename" from the pop-up menu. Keep the original file name, but add an extension like ".old" or ".orig" to indicate that it is the original file.
Rename the new.pst file by right-clicking on its icon and selecting "Rename" from the pop-up menu. Edit the file name to match the original file name.
Start the hex editor software you installed in Step 2 and use it to view and edit the backup copy of the .pst files. Save and exit the hex editing program when you have finished editing the backup file.
Restart Outlook to see if the edits you made solved the problem and prevented additional error messages. Check all your data within Outlook to make sure it is intact. If the problems remain, repeat Step 8 as needed. Revert the original .pst files back to their original file names if necessary by right-clicking on their respective icons and selecting "Rename" from the pop-up menu.
Use extreme caution when editing Outlook .pst files. Errors can result in loss of your data.