Cannot Install Service Pack 6/6a with High Encryption Internet Explorer

[ATC]

If you attempt to install the standard-encryption (or 56-bit) version of Windows NT 4.0 Service Pack 6 or 6a on a Windows NT 4.0-based computer that already has Microsoft Internet Explorer High Encryption Pack or Internet Explorer version 5.5 installed, you receive the following error message:

   You have chosen to install a version of the Service Pack
   with Standard Encryption onto a system with High Encryption.
   This is not supported.
   To successfully install this version of the Service Pack,
   you must install the High Encryption version.
   Press Help for more information about obtaining the High
   Encryption Version of this Service Pack. Service Pack Setup
   will now exit.



CAUSE
This issue occurs because the Schannel.dll file that is installed by Microsoft Internet Explorer High Encryption Pack and Internet Explorer 5.5 cannot be overwritten by the service pack installation program.

Internet Explorer 5.5 includes 128-bit encryption by default because of the United States government's recent decision to allow companies to export products that use strong, 128-bit encryption.

Windows NT 4.0 Service Pack 6 and 6a were released before this decision was made. Therefore, localized versions of Service Pack 6 and 6a are 40-bit versions. 40-bit versions of these service packs detect higher encryption levels and do not allow themselves to be installed.

[ATC]

To work around this issue and prevent the version-number scanner from comparing the Schannel.dll file versions:

1. Use any text editor (such as Notepad) to open the Update.inf
   file in the I386\Update folder in the service pack source
   files.


2. Place a semicolon ( before the reference to the
   Schannel.dll, Security.dll, and Ntlmssps.dll files in the
   [CheckSecurity.System32.files] section of the Update.inf
   file.


3. Save and then close the Update.inf file.


4. Install the service pack.