I've installed Internet Explorer 5.01 international version with high encryption now I can't install SP6a?

A. If you attempt to install the standard-encryption version of Windows NT 4.0 Service Pack 6a (SP6a) on a Windows NT 4.0-based computer that already has Microsoft Internet Explorer High Encryption Pack installed, you may 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.

This happens because the Schannel.dll file that is installed by Internet Explorer High Encryption Pack cannot be overwritten by the service pack installation program.

To workaround this perform the following:

  1. Start a text editor (such as Notepad)
  2. Open the Update.inf file in the Service Pack 6a folder
  3. Remove the reference to the Schannel.dll file from the \[CheckSecurity.System32.files\] section
  4. Save the file
  5. Now install SP6a!

An alternative method which you may find quicker is:

  1. Take a copy of schannel.dll from another NT4 machine without high encryption
  2. Rename the schannell.dll on the maschin with high encryption to schannel.dll_high
  3. Place your low encryption schannel.dll into your system32 folder
  4. Install SP6a
  5. Reboot your machine
  6. Now you can remove schannell.dll safely and replace with the saved schannel.dll_high

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