Create image files of the 3 CD's with Imgburn (or any software that can create ISO or BIN/CUE files). When a game has more than one CD, it's usually best to create image files. You will then need to use the "imgmount" command instead of "mount".
Here's exactly how I installed and run Zork Nemesis, if it helps at all:
Some of this will be more information than you need, but maybe the additional details will help someone else some day.
I almost never play a DOS game using the CD (or CD's), but sometimes I install the game using the CD.
I usually make BIN/CUE files, because those images will include CD Audio, if any were on the CD.
Zork Nemesis does not contain CD Audio, so ISO files should be fine.
The image files I created are called:
zn1.cue
zn1.bin
zn2.cue
zn2.bin
zn3.cue
zn3.bin
In Windows, I created a folder called "dosgames" on my C drive.
In the "dosgames" folder, I created a folder called "zncd".
I placed these 6 files in that folder (c:\dosgames\zncd).
In DOSBox, I installed the game from the real CD (Disc 1) using these commands:
mount c c:\dosgames
mount d e:\ -t cdrom
d:
cd dos
install
(My actual CD drive is drive E. If yours is different, change "e:\" to the drive letter of your actual CD drive)
I installed the game to "c:\znemesis" (Of course, when you exit DOSBox, you'll see that this folder is actually "c:\dosgames\znemesis" in Windows)
Then I put the CD's in a safe place.
I launch the game with these commands:
mount c c:\dosgames
imgmount d "c:\dosgames\zncd\zn1.cue" "c:\dosgames\zncd\zn2.cue" "c:\dosgames\zncd\zn3.cue" -t iso
c:
cd znemesis
zorkdos
Then I can cycle through each disc using Ctrl-F4. If I type Ctrl-F4 three times, it would cycle back to disc 1.
Of course, these commands can be put in the [autoexec] portion of the configuration file (dosbox-0.74.conf). The only other changes I made to the config file are fullscreen=true and cycles=max.
I like to copy the config file to my game folder (in this case, "c:\dosgames\znemesis"). Then I copy the shortcut to DOSBox to my desktop, rename the icon to Zork Nemesis, and right-click on the shortcut and select "Properties". Then I change the "Target" box to look like this:
"C:\Program Files\DOSBox-0.74\dosbox.exe" -conf "C:\dosgames\znemesis\dosbox-0.74.conf"
By the way, when a game comes on several CD's, try to make the folder and file names short, because the IMGMOUNT command can only handle so many characters. I'm not sure exactly how many. I had a problem with Wing Commander IV (6 CD's), until I figured this out.
If I made ISO files, I would only have 3 files:
zn1.iso
zn2.iso
zn3.iso
and I would launch the game like this:
mount c c:\dosgames
imgmount d "c:\dosgames\zncd\zn1.iso" "c:\dosgames\zncd\zn2.iso" "c:\dosgames\zncd\zn3.iso" -t iso
c:
cd znemesis
zorkdos