Open the Stargunner DOS Config and change the settings to the following:

[sdl]
fullscreen=false
fulldouble=false
fullresolution=Fixed
windowresolution=original
output=opengl
autolock=true
sensitivity=100
waitonerror=true
priority=higher,normal
mapperfile=mapper-0.74.map
usescancodes=true

[cpu]
core=auto
cputype=auto
cycles=max
cycleup=10
cycledown=20

[autoexec]
# Lines in this section will be run at startup.
# You can put your MOUNT lines here.

@echo off
Mount C ".."
C:
cls

then save your config file.

If you want to switch back to Stargunner, change the Following in your STARGUN DosBox Config File:
[autoexec]
# Lines in this section will be run at startup.
# You can put your MOUNT lines here.

@echo off
Mount C ".."
C:
cls
Stargun.exe

[cpu]
core=auto
cputype=auto
cycles=30000
cycleup=10
cycledown=20

Download & Install PowerISO then set the virtual CD drives to 1 (up to a max of 23) & mount the CD Image to that virtual drive or place a DOS CD-ROM into your computer.

Open DOSBOX & mount the virtual drive then add -t cdrom.

Open the installation program and follow the instructions show for installing the game and setting up the sound & music for that game.

Launch the game. (NOTE: You may need to switch CDs, just in case & you'll need to the CD-ROM to play the game, otherwise the game won't start up.)