IdenSwitch

From NirSoft:

Starting from version 5.0, Outlook Express allows you to create multiple identities, where every identity has a separate address book, inbox and other folders. However, in order to switch to other identity, you have to open Outlook Express with the current identity, select 'Switch Identity' from the File menu, and then select the desired identity.
This utility allows you to instantly open Outlook Express with the desired identity, without opening Outlook Express at first. It provides 2 methods to do that:

• You can simply select the desired identity from the main window of IdenSwitch, and then click the 'Switch' button.
• You can create special shortcuts on your desktop that will instantly open Outlook Express with the desired identity.