Windows Installer Cleanup utility  (XP and Vista)

Trying to uninstall a program you never use anymore and Windows won't let you because some of the installation information is corrupt.
Fortunately, Microsoft has a tool for removing installer information from especially pesky programs. Keep in mind, the Windows Installer Cleanup Utility this is not a tool to replace the Windows Add/Remove programs utility in the Control Panel. What the utility does is remove Windows Installer configuration information.
Running the utility should bring up a list of programs that were installed using the Windows Installer. Select the application you want to clear and click remove. The installer info for that program should disappear, but the program will not.
In other words, use this program if Windows thinks that a program is installed but it is not. Do not use it to remove programs. It won't do that. Theoretically you could use this application to prevent yourself from accidentally removing programs. If there's no installer information, there's no uninstall option in your Add/Remove settings.