Windows installer is one of the best and worst things about developing on Windows. It's great that there's a unified, supported installation mechanism compared to Linux with the different package managers etc, but at the same time it's a royal pain to learn and use properly. I'd hazard a bet that a fair majority of the installs out there (mine included!!) are pretty sub-par, and not up to scratch.

To that end, the Windows Installer Search Engine should be a great resource to try and gain an insight into the frustrating world of Windows Installer.