Since I couldn't use alt+tab to switch between Gabriel Knight 3 and other applications in Windows 7, I developed a small minimizer so I could minimize the game using a hotkey combination. It's user configurable and doesn't require .NET or anything other than the OS. I initially made it for my personal use, but if you also want to use it, just download it from http://www.filedropper.com/gk3minimizer
It should be compatible with any version of Windows, but I haven't tested it under Windows 95 or 98.
Can't wait 'till the 20th Aniversary editon!