It is better to be safe than sorry!

0. Read the Readme.txt file.

1. Perform a full backup of files and registry.

2. Update the emergency repair disk (ERD). Run rdisk /s.

3. Shutdown and restart your system, checking the Event Viewer for errors. Resolve these before installing SP4.

4. Move your previous Uninstall directory to a different folder. This directory is normally located at
    %SystemRoot%\$NTServicePackUninstall$.

5. Run Srvinfo.exe from the Windows NT resource kit and document existing hotfix information or see tip 068
    After you are sure you will not be uninstalling SP4, you can remove the previous hotfix information.

6. Disable any non-essential third-party drivers and services. Contact the vendors for updated versions.

7. Verify available disk space. SP4 requires ~40 MB (~80 MB if theUninstall option is chosen).

8. Close all applications, active debugging sessions and remote control sessions before starting the install.