Not Necessary to Reinstall Windows 2000 Service Packs After System State Changes

After you change the system state by adding or changing additional Windows 2000 components, you do not need to reapply Windows 2000 service packs.

When you install a Windows 2000 service pack, the Update.exe tool performs the following actions:

• The Layout.inf file is updated with an additional source for Windows 2000 service pack files so when you add or change additional components the Layout.inf file points to the correct source. The source location is stored in the following registry key:
  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup\ServicePackSourcePath
  The source could be a network share of the Windows 2000 service pack, the Windows 2000 service pack CD-ROM, or if you install the Windows 2000 service pack by using the Express Installation from the Web, the source is set to the %systemroot%\servicepackfiles folder.
• Windows 2000 service packs also update the Drvindex.inf file to point to an additional .cab file for drivers that are updated in the Windows 2000 service pack. The name of this .cab file is Spn.cab (where n is the service pack version number) and this file is installed to the %systemroot%\driver cache\i386 folder.
• A new Spn.cat file (where n is the service pack version number) is also installed for the updated files. This replaces any previously installed Spn.cat file that was installed with a Windows 2000 hotfix. The Spn.cat file is installed to the %systemroot%\system32\CatRoot\{F750E6C3-38EE-11D1-85E5-00C04FC295EE} folder.
• Hotfixes do not update the Layout.inf file. Therefore, if you install a hotfix and system state changes occur, you may need to reapply the hotfix.

Windows 2000 service packs also perform version checking on files so that post Windows 2000 SPn hotfixes (where n is the service pack version number) remain in place and do not need to be reapplied after installation of the service pack. For example, hotfixes prior to Windows 2000 Service Pack (SP1) are updated to the service pack files.