The Windows Installer is a program for the installation, maintenance, and removal of software on your Microsoft Windows computer.
The installation information, and often the files themselves, are packaged in installation packages, freely relational databases structured as OLE Structured Storage Files and commonly known as "MSI files", from their default file extension.
New features include a GUI and automatic generation of the uninstaller sequence. Windows Installer is positioned as an alternative to stand-alone executable installer such as older versions of Install Shield and Wise (later versions of both products are based on Windows Installer).
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"Microsoft encourages third parties to use Windows Installer as the basis for installation frameworks, so that they synchronize correctly with other installers and keep the internal database of installed products consistent. Important features such as rollback and version depend on a consistent internal database for reliable operation."
Most of the software install in your computer will use windows installer, but not all.
I would say about 80% use windows installer and 20% have there own installer.
That is why we have windows installer problems or windows installer not working properly.
How to use the Windows Installer Cleanup Utility to remove software
If you can’t remove or uninstall a software in Windows using either the Uninstall option or the Add/Remove Programs tool, then you could try the Windows Installer Clean Up Utility.
As long as you installed the application using the Windows Installer,Witch is done automatically this utility will remove all the folders, files, registry keys, and entries from your system and allow you to start over with a clean slate.
2. Run the msicuu2.exe file you downloaded to install the Windows Installer Clean Up Utility.
3. Launch the Windows Installer Clean Up Utility from the Start menu.
4. Within Windows Installer Clean Up Utility screen box, locate the application in the list you want to remove and click the Remove button.
5. Once the application has been removed, click the Exit button to close the utility. The application should now be completely removed from your Windows XP computer system.