Microsoft Knowledge Base Article 896658 contains the following introduction:

Microsoft Windows 2000 Service Pack 4 (SP4) contains an update to the License Logging service. Part of this update is to help prevent anonymous connections to the License Logging service by removing the License Logging Service Remote Procedure Call (LLSRPC) from the NullSessionPipes registry key.

NullSessionPipes is initialized during installation of Windows 2000, according to Netserv.inf. Netserv.inf is a file that controls configuration of the Server service. The Server service supports file, print, and named-pipe sharing over the network.

You can install a service pack by using one of the following methods:

Update the existing software from a prior service pack (an “update” installation).
Install from a CD or a network share with the service pack files integrated into the CD or network share.

The SP4 update installation applies the update to NullSessionPipes by directly changing the registry key during installation.

The SP4 update package does not include the new version of Netserv.inf. Therefore, when SP4 is used to build an integrated, or slipstream, installation, it does not replace the original Netserv.inf file. In an integrated installation, the NullSessionPipes registry entry includes LLSRPC.

Note Integrating a service pack into another set of files that you want to install is known as slipstreaming.

If you are running an operating system that was installed by using an integrated CD or a network share, you can follow the steps that are provided in this article to change the registry directly. If you want to fix a network install share, you can follow the steps to update the Netserv.inf file. If you are installing from an SP4-integrated CD, you must make the change in the registry after the installation.