Sierra probably isn’t going to help you since they don’t support those games anymore. It sounds like you’re trying to run a Windows executable instead of a DOS executable. Did you already install it? There are two install programs, setup.exe is a Windows file and install.exe is a DOS file. The CD should have both versions, Windows and DOS versions of KQ5. If you want to install the DOS version, you need to run the proper install file, which is probably install.exe or install.bat in the KQ5 directory.