In the event that Outlook has become unuseable or you just need a fresh start, you can rename the associated dat files to set everything back to factory defaults. 

– Unfortuantely, this does not work in Outlook 2010.

Before we begin, you’ll want to make sure that you can see extensions…

Browse to control panel > folder options > click the “view” tab > uncheck “hide extensions for known file types” and bullet “show hidden files, folders, and drives”.  Then Click “apply” and “OK”.

Close Outlook before making the following changes.

To reset toolbar customizations:

 WinXP

– Browse to C:Documents and Settings%username%Application DataMicrosoftOutlook

– Rename “outcmd.dat” to “outcmd.old”

WinVista/Win7

– Browse to C:Users%username%AppDataRoamingMicrosoftOutlook

– Rename “outcmd.dat” to “outcmd.old”

To reset add-ins and extensions

WinXP

– Browse to C:Documents and Settings%username%Application DataMicrosoftOutlook

– Rename “extend.dat” to “extend.old”

WinVista/Win7

– Browse to C:Users%username%AppDataRoamingMicrosoftOutlook

– Rename “extend.dat” to “extend.old”

Open Outlook, wait until the fizz subsides, and enjoy the freshness!