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Repairing the Windows installer

Why it goes bad, and how to fix it.

Windows 2000 contains a system component, the Windows Installer, which is billed as an "application installation and management service." Many non-Microsoft products rely on it as well, and it is used to install and manage .MSI packages, a software-distribution format that can be used by sysadmins to distribute programs to many desktops at once.

There are two extant versions of the installer. Version 1.1 ships with Windows 2000 on the installation CD-ROM. Version 2.0, however, ships with Windows XP, .NET Server, and is also packaged with Windows 2000 Service Packs 1 and 2. When the Service Packs are applied, the Installer is upgraded to the 2.0 version. Since it's considered a fairly integral system component, like DirectX, this is not intended to be a reversible action. (The 1.1 revision of the Installer also had some issues that have required an update.)

Under certain combinations of circumstances, however, it is possible to damage the installer. If Service Packs 1 or 2 are installed, and then removed, programs that depend on the Windows Installer may no longer function correctly, or you may be prompted to reinstall them. This is because two things happen when you upgrade the Windows Installer to the 2.0 version:

  1. the binaries for the installer are updated, and
  2. the program databases, which contain the information about each program installed with Windows Installer, are converted from the 1.1 format to the 2.0 format. The 1.1 version of the Installer cannot read the 2.0 format files, and so the program assumes the installation is corrupt and must be redone.

Fortunately, it is easy enough to get around this problem. Microsoft packages Windows Installer 2.0 separately as a redistributable download. If you have removed a Service Pack or performed some other action that cause the Installer to revert to the 1.1 revision, upgrade to the 2.0 version of the installer apart from any other changes you may make. The Installer can be downloaded from

If you want to find out if you have the 2.0 revision already installed, look for the file MSI.DLL in %SystemRoot%system32 and check its revision number in the Properties window. If MSI.DLL is version 2.0.2526.0 or later, you have the 2.0 edition of the Installer already present.

Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter.

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