Reinstalling IE and Outlook Express

Locate the appropriate registry subkey, right-click the IsInstalled (REG_DWORD) value, and then click Modify. To reinstall only the Internet Explorer 6 browser component on Windows XP, use the following registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{89820200-ECBD-11cf-8B85-00AA005B4383}

To reinstall only Outlook Express 6 on Windows XP, use the following registry key: 

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{44BBA840-CC51-11CF-AAFA-00AA00B6015C}