Mount your CD drive in DOS-Box, and run the installer from there.
From the DosBox manual:-
"To mount your CD-ROM in DOSBox you have to specify some additional options
when mounting the CD-ROM.
To enable CD-ROM support (includes MSCDEX) in Windows:
- mount d f:\ -t cdrom
"In some cases you might want to use a different CD-ROM interface,
for example if CD audio does not work:
To enable SDL-support (does not include low-level CD access!):
- mount d f:\ -t cdrom -usecd 0 -noioctl
To enable ioctl access using digital audio extraction for CD audio
(windows-only, useful for Vista):
- mount d f:\ -t cdrom -ioctl_dx
To enable ioctl access using MCI for CD audio (windows-only):
- mount d f:\ -t cdrom -ioctl_mci
To force ioctl-only access (windows-only):
- mount d f:\ -t cdrom -ioctl_dio
To enable low-level aspi-support (win98 with aspi-layer installed):
- mount d f:\ -t cdrom -aspi
explanation: - d driveletter you will get in DOSBox (d is the best,
don't change it!)
- f:\ location of CD-ROM on your PC. In most cases it will
be d:\ or e:\
- 0 The number of the CD-ROM drive, reported by "mount -cd"
(note that this value is only needed when using SDL
for CD audio, otherwise it is ignored)
See also the next question: The game/application can't find its CD-ROM."
Hope this is of some help.