We have an installshield 12 package that when used in certain Windows XP environments, causes the MS Installer to start and try to install another unrelated software program whenever users launch our application. The application the Windows installer is trying to install is AutoCAD, a completely unrelated product of which our software knows nothing about. The Windows Installer Cleanup Utility does fix the problem unless AutoCAD installation or our installation is run again. This issue happens in only one site and no other instance of our installation has cause such an issue.
Research has suggested that the registry is locked down and the MS Installer cannot write the necessary registry entries to complete the installation properly. I have not been able to confirm this.