Try this
http://www.softpedia.com/get/Security/S ... lity.shtml
It's the pukka Microsoft Windows Installer Clean-up utility, not often advertised...wonder why not
Here's a little snip of the readme
README FOR WINDOWS INSTALLER CLEAN UP UTILITY
DECEMBER 2003
WHAT IS THE WINDOWS INSTALLER CLEAN UP UTILITY?
The Windows Installer Clean Up 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 corrupt
- You or someone else inadvertantly 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"