I have just updated my Microsoft Office suite from 2003 to 2007. When I did so many of my archived emails were lost. These were stored in Microsoft Outlook. Upon researching this I discovered that this often occurs upon upgrading Office. I further learned that when this happens you must immediately get hold of a program email recovery specifically designed to recover deleted emails on Outlook. While my files were not deleted per se, they still had gone missing. Outlook archived files use the file extension .pst. This is an extension created just for Outlook.
It seems that during the upgrade some file can lose the data for their extensions or even have the extension changes involuntarily. The solution to this is simple. Download REMO Outlook Repair Program. This powerful data recovery utility will scan your entire hard disk in seconds to find any missing .pst files. These can then be resaved or written to disk.