Disk 0 is the startup disk, used to begin installation.

NOTE: For some reason, Sierra's original installation/configuration program for SQ4 EGA does not work when installing files directly from the floppy disks. The best course of action is to copy the contents of each disk manually to the desired installation folder. Before starting the game, run INSTALL.EXE to configure the game's sound and video options. (Be sure to skip the step where the installer asks you to select a hard drive for installation.)