Microsoft has created the Windows Installer CleanUp Utility, which allows you to safely remove Windows Installer-related registry settings from your computer in the event of a problem. This utility from Microsoft allows you to clean out applications from the Microsoft Installer local database. If you ever get an app (that uses the MSI) that gets so screwed up you can't uninstall it, can't reinstall it, and you are stuck, this application should allow you to tackle the problem. Once installed, you run the program "Windows Install Cleanup" from your Start menu. It will bring up a list of installed applications that use MSI. You can then remove any of them from the MSI database. The Windows NT version of the Windows Installer CleanUp Utility is Msicuu.exe, the Win9x and ME version is Msicu.exe. Check Q238413 for links to download the utility. The contents of the readme.txt file:

          --------------------------------------------
          README FOR WINDOWS INSTALLER CLEANUP UTILITY
                          JUNE 1999
          --------------------------------------------

WHAT IS THE WINDOWS INSTALLER CLEANUP UTILITY?
----------------------------------------------

The Windows Installer CleanUp Utility is designed to allow you to safely 
remove Windows Installer settings from your computer in the event of a 
problem. Although the Windows Installer is designed to be very robust, it 
is possible for Windows Installer to become damaged if:

 - Your computer's registry becomes corrupted.
 - You or someone else inadvertently changes a registry setting used by the 
   Windows Installer, resulting in a problem.
 - The installation of a program that uses Windows Installer (for example, 
   Microsoft Office 2000) is interrupted.
 - There are multiple instances of Setup running simultaneously, or an 
   instance of Setup is "blocked."

WHY ARE THERE TWO VERSIONS?
---------------------------

There are two versions of the Windows Installer CleanUp Utility: Msicu.exe 
is designed for use in Windows 95 and Windows 98, and Msicuu.exe is 
designed for use in Windows NT. If you attempt to run the incorrect version 
of the Windows Installer CleanUp Utility for your operating system, you 
will receive an error message, and the Windows Installer CleanUp Utility 
will not proceed.

WHAT IS MSIZAP.EXE?
-------------------

Both versions of the Windows Installer CleanUp Utility make use of the same 
file, Msizap.exe, to perform cleanup operations of the Windows Installer 
registry settings. It is not recommended that you manually run Msizap.exe, 
because it uses a command-line interface and does not provide the same ease 
of use or level of protection as the Windows Installer CleanUp Utility.

HOW DO I INSTALL THE WINDOWS INSTALLER CLEANUP UTILITY?
-------------------------------------------------------

When you download the Windows Installer CleanUp Utility, simply run it. By 
default, the Setup program will install the Windows Installer CleanUp 
Utility's files to the following folder on your hard disk:

   C:\Program Files\Windows Installer CleanUp

Note that you can install to another location if you so choose. All of the 
files used by the Windows Installer CleanUp Utility (Msicu.exe, Msicuu.exe, 
Msizap.exe, and this Readme file) are copied into this folder. A shortcut 
for the Windows Installer CleanUp Utility will be created on the Start 
menu, (point to Programs, and click Windows Installer CleanUp).

Note that if you attempt to install the Windows Installer CleanUp Utility 
from a floppy disk, you may receive the following error messages:

   Internal Error 2724. UNINSTALL 1,

   Installation ended prematurely because of an error.

To prevent this problem from occurring, only install the Windows Installer 
CleanUp Utility from your hard disk.

HOW DO I RUN THE WINDOWS INSTALLER CLEANUP UTILITY?
---------------------------------------------------

To run the Windows Installer CleanUp Utility, use either of the following 
methods:

 - Click the shortcut for the Windows Installer CleanUp Utility on the 
   Start menu.

   -or-

 - In Microsoft System Information, click Windows Installer CleanUp on the 
   Tools menu.

When you do this, a dialog box containing the following message will 
appear:

   Continuing further will make permanent changes to your system. You may
   need to reinstall some or all applications on your system that used the
   Windows Installer technology to be installed. If you do not want to 
   proceed, please press the 'Exit' button now. Choosing 'Remove' will make 
   the permanent changes.

The dialog box lists all programs that are installed on your computer that 
use Windows Installer. Because the Windows Installer CleanUp Utility also 
uses Windows Installer, it will be listed in this dialog box.

Note that you can select multiple items in the list by holding down SHIFT 
or CTRL while you select the items.

There are four buttons:

   Select All   Selects all programs in the list.

   Clear All    Unselects all programs in the list.

   Remove       Removes the Windows Installer registry settings associated
                with the selected program(s).

   Exit         Exits the Windows Installer CleanUp Utility.

If you click Remove, the Windows Installer CleanUp Utility will prompt you 
with the following message:

   Warning - All items selected will be removed from the Windows Installer 
   database. In order for the items to work properly, you must individually 
   re-install all items selected. Select OK to continue removing product,
   Cancel to abort.

If you click OK, the Windows Installer CleanUp Utility will remove all 
Windows Installer registry keys associated with the selected programs, 
including the entries for the programs in Control Panel under Add/Remove 
Programs. If you remove the settings for a program that is currently 
installed on your computer, the program will no longer be able to add or 
remove components or to repair itself. To prevent problems, it is 
recommended that you reinstall your programs before you use them.

WHAT IF I RECEIVE AN ERROR MESSAGE?
-----------------------------------

The Windows Installer CleanUp Utility is designed to inform you if there is 
a problem. The following table lists the error messages that may be 
displayed by the Windows Installer CleanUp Utility and their causes:

   Error Message                            Cause
   ------------------------------------------------------------------------

   Could not remove Microsoft Office 2000   Msizap.exe could not be found, 
   Troubleshooters (All Users) (error       or could not be launched by the 
   launching msizap.exe: 2)                 Windows Installer CleanUp 
                                            Utility

   You must have Administrator rights to    In order to run Msicuu.exe, you 
   run this utility.                        must be logged on with 
                                            administrative rights.

   This is the Windows 98/95 version of     If you are running Windows NT, 
   the Installer Clean Up Utility and       you should run Msicuu.exe.
   will not run on Windows NT.

   This is the Windows NT version of the    If you are running Windows 95 
   Installer Clean Up Utility and will      or Windows 98, you should run 
   not run on Windows 98/95.                Msicu.exe.

DOES THE WINDOWS INSTALLER CLEANUP UTILITY CREATE A LOG FILE?
-------------------------------------------------------------

When you run the Windows Installer CleanUp Utility, it creates a log file 
named Msicu.log in your Windows\Temp folder. You can use this log file to 
determine what programs the Windows Installer CleanUp Utility has removed 
from your system, and support engineers can use the log file to determine 
if the Windows Installer CleanUp Utility has successfully uninstalled a 
program. Please note that the log file is cumulative; each time you use the 
Windows Installer CleanUp Utility, it appends new information to the log 
file.

HOW DO I UNINSTALL THE WINDOWS INSTALLER CLEANUP UTILITY?
---------------------------------------------------------

When you install the Windows Installer CleanUp Utility, it creates an entry 
for the Windows Installer CleanUp Utility in Control Panel under Add/Remove 
Programs. To remove the Windows Installer CleanUp Utility, select the item 
in the list of installed programs and click Add/Remove. 

A must for support and installations personnel as well as technical savvy users. 1800 pages with a wealth of information on the CD.