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For information about the differences between Microsoft Outlook Express and Microsoft Outlook e-mail clients, click the following article number to view the article in the Microsoft Knowledge Base:
257824 OL2000: Differences Between Outlook and Outlook Express
IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:
256986 Description of the Microsoft Windows Registry
Outlook Express does not start when you click theMail button, and then click Read Mail in Microsoft Internet Explorer. Outlook Express is verified as installed and starts from the Run dialog box. Additionally, it may not be listed as an available e-mail program in Internet Explorer's Internet Options.
This behavior can occur because of missing or invalid registry key entries.
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
Make sure that the following registry keys are in place and have the correct values. You may need to add them or parts of them. To start Registry Editor, click Start, and then click Run. In the Open box, type regedit, and then click OK.