If you notice that Outlook Express takes a lot more time to load and start,maybe it's because you changed or disabled Windows Messenger.Outlook Express is closely related to Windows Messenger and if it has been disabled you might have to disable the Contact pane on the Outlook main window.
Here few easy steps to do the job:

1. Open Outlook Express
2. Click on View > Layout





3. Remove the  Contacts
4. click Apply
5. Click OK

     If you want to keep your Contact Pane then it becomes a little more complicated because you will have to edit the Windows registry.I strongly recommend to back up your Registry file before you start editing it,because it,s a very delicate and important Windows file and,if something goes wrong ,Windows might not run properly any more.
                        To back up the Windows Registry do This

• Click Start, and then click Run



• In the Open box, type regedit, and then click OK.



• Locate and then click the subkey that contains the value that you want to edit.



• On the File menu, click Export



• In the Save in box, select a location where you want to save the Registration Entries  



• (.reg) file, type a file name in the File name box, and then click Save.
  Do not follow these steps to export a whole registry subtree. (HKEY_CURRENT_USER is an example of such a subtree.) If you must back up whole registry subtrees, back up the whole registry instead. For better advise on how to back up the Registry go to the Microsoft Support Page
       http://support.microsoft.com/kb/322756

        Now if you want to edit your Windows Registry follows these steps:

1.  Click Start, and then click Run
2. In the Open box, type regedit, and then click OK.





3. This is the Windows Registry,as I said earlier you must back up this file before editing it.In the left Pane expand the HKEY_LOCAL_MACHINE by double-clicking on it,scroll down the new column of registry keys to Software and expand it,another long list appear,find Microsoft and expand that as well,on the new column go down to Outlook Express and select it by clicking on it.
4. Click Edit > New > DWORD




5. On the Right window a new value appears, rename it Hide Messenger




6. Double click on it after rename it and under the Value Data type 2 and click OK
7. Close the Registry Editor by clicking the X button