Outlook Won't Start!

Q: When I try to start Outlook it just immediately gives me an error message: Cannot Start Outlook.

A: First off, try starting Outlook in Safe Mode.  You do that by holding down the CTRL key while clicking the Outlook icon to start it.  If that works then the problem is probably a misbehaving add-in. 

In Outlook 2007 go to Tools | Options | Other | Advanced and click the COM Add-Ins button...
In Outlook 2010 go to File | Options | Add-ins...

...and disable/uninstall any add-ins you don't need.  If that doesn't help, go back in and disable the add-ins you think you do need, and re-enable them one-by-one until you find the one causing the problem.

If that doesn't work then try starting Outlook with the /resetnavpane switch.  To do that, click Start | Run and type:

Outlook /resetnavpane

Note that there is a space between the "k" of Outlook and the "/".