After installing the Windows 2000 Service Pack 2 (SP2), your system may still show that Service Pack 1 (SP1) is installed in the Add/Remove Programs list. This neither affects how Windows 2000 runs nor impacts SP2 and its function. However, you might want to remove the SP1 entry from Add/Remove Programs to unclutter the list and to prevent curious end users from deleting the service pack you just installed.
Word of warning
The following section suggests ways to edit your System Registry. Using the Windows Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system and could result in data loss. TechRepublic does not and will not support problems that arise from editing your registry. Use the Registry Editor and the following directions at your own risk.
It's all in the Registry
One task that Setup performs when you install SP1 is to make a change to the registry to indicate that SP1 is installed. The entry is added to the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Current
Version\Uninstall. When you open the Add/Remove Programs item in the Control Panel, you'll see that SP1 is one of the applications listed in that registry key.
To remove SP1 from the Add/Remove Programs list, open the Registry Editor, expand the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Current
Version\Uninstall key, and delete the entry for Service Pack 1 (see Figure A).
While this key is open, review it for other applications that you need to properly remove. Just remember that once a program is removed from the Add/Remove Programs list, you won't be able to uninstall it using Add/Remove Programs. Instead, you’ll have to remove it manually by deleting its registry keys (if it has any) and its directories and files.