By default, Outlook places each Offline Folders (.ost) file and Personal Folders (.pst) file that it creates in the %userprofile%\Local Settings\Application Data\Microsoft\Outlook folder. This setting allows you to change the default behavior and store the files in any folder.

Open your registry and find the appropriate key below.

Outlook 2010 – [HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook]

Outlook 2007 – [HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook]

Outlook 2003 – [HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook]

Outlook XP – [HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook]

Outlook 2000 – [HKEY_CURRENT_USER\Software\Microsoft\Office\9.0\Outlook]

Create a new REG_EXPAND_SZ (Expandable String) value called ‘ForcePSTPath’ and set it to equal the full path of the required personal folder directory (e.g. “C:\Mailbox”).

Restart Outlook for the change to take effect.

Note: This is a expandable string value so you can use environment variables, such as %userprofile%, to specify the path. When the value does not exist the default value of “%userprofile%\Local Settings\Application Data\Microsoft\Outlook” is used.