If you remove Windows 2000 Service Pack 1, or Windows 2000 Service Pack 2, after installing Windows Installer version 2.0, you will be prompted to reinstall any program that used the Windows Installer?
Removing the Service Pack in the above situation restores the Windows Installer files to version 1.1. Version 1.1 files can NOT read the version 2.0 database, causing the prompt.
To resolve this issue:
1. Press Cancel when you are prompted to reinstall.
NOTE: If the version of Msi.dll file is Version number 2.0.2526.0 or later, you have Windows Installer 2.0 installed.
Released Versions of Windows Installer.