Microsoft Knowledge Base Article 263837 contains the following summary:
This article describes how to manually remove and then reinstall Microsoft Outlook Express 5.x and 6.0 on a computer that is running Microsoft Windows 2000, Windows XP Home Edition, or Windows XP Professional.
• The purpose of the steps in this article is to repair the functionality of Microsoft Outlook Express if the program installation is damaged.
• If you need to remove and reinstall Outlook Express 6.0 in Windows 2000, use the "Add/Remove Programs" tool in Control Panel first. If you are not successful with this method, you should proceed with the remaining information in this article.
• Do not apply this procedure to Domain Controllers without reinstalling Outlook Express. Active Directory will call Component Data Object Interfaces which will be broken when these steps are executed.
• Outlook Express should not be removed as a permanent solution to a problem that is being investigated. If you remove Outlook Express, it will impair the functionality of Microsoft Outlook. If you remove Outlook Express, you must reinstall it. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
230076 Outlook 2000 requires Outlook Express
• When you troubleshoot Outlook Express issues on any Windows computer, the following files should never be renamed unless you are replacing them with later versions. These files are core Windows components. The files are as follows:
Removing these files will result in an unsupported Windows configuration. Additionally, removing these files can result in problems with other applications. For instance, MimeOLE functionality is dependent on the Inetcomm.dll file.
• This article does not apply to Microsoft Windows Server 2003.
Note Before you remove Outlook Express, make sure you are logged on to the computer with administrative rights.