If you use Outlook 2007 and you suddenly get this error…
Cannot start Microsoft Office Outlook. Unable to open the Outlook window
…then you may need to reset the navigation pane in Outlook.
1) Close Outlook and any email windows you have open
2) In Windows XP click Start then choose Run. In Windows Vista and 7 just click Start and type the following in to the search box.
3) Now type OUTLOOK /RESETNAVPANE and hit enter.
Outlook should now open up. You will have lost any modifications to the navigation bar on the left hand side but otherwise you will be good to go.
