The game believes that it's installed to D:\Holmes2, but, when the batch file tries to change to that directory, that directory doesn't exist. Next, when it tries to run the executable for the game, it can't find it, because the "change directory"/CD command failed, so "Illegal command" is returned. You need to either fix your drive mounts in DOSBox/D-Fend or edit Holmes2.bat to compensate. It'd probably be easier to simply edit Holmes2.bat.

Try this. Replace everything in Holmes2.bat with the following:

@echo off
Set DOS4GVM=DELETESWAP MAXMEM#8192 SWAPNAME#.\MYTHOS.SWP
HOLMES2 .\MYTHOS.CFG %1 %2 %3

That eliminates the unnecessary directory references. Make sure that that Holmes2.bat is in the same folder as Holmes2.exe and is what D-Fend is set to run in order to launch the game.

BTW, you don't even need to mount the ISO in DOSBox. The whole installed game is in the Holmes2 folder on the CD, so you can simply copy that to a folder on your hard drive, run install.exe from it, give it the folder that you're running it from, then run Setsound.exe to set your sound cards.

Osprey,

Thanks for your reply, I appreciate it.

After a few hours of banging my head on the desk, shortly after I posted this I came across the solution. I had long thought it was a problem with the drive mounts and so I checked the "drive" settings in the game's profile again. I noticed the CD image was mounted to a 3rd drive labeled "E" whereas the game was trying to start in the virtual CD drive mounted as "D." I removed "E" altogether and set "D" as the CD image. That fixed the problem.

The question I have is why D-fend reloaded would naturally set this up incorrectly? The impression I had of D-fend was that it was supposed to make these things easier, not harder. 😕

One last thing. This is a game from 1996 which means it has a 4:3 resolution, and I'm seeking to emulate that aspect ratio, even if it means black bars. But the only resolution that can be feasibly used on my 16:9 widescreen monitor is fullscreen, which fills in the whole space. It doesn't look "bad" but I imagine it is scaled up or stretched, right? I tried all the other 4:3 resolutions (e.g. 1280x960) with aspect ratio set to ON, but in every case the image is very small.

Maybe I'm just an idiot again. On the other hand, as it plays now, the text boxes in-game stretch across the whole screen making for some annoying reading.. it doesn't seem quite right..? 😲

I've never used D-fend, so I can't really help you with that, but you need to enable aspect ratio correction. In DOSBox's .conf, that can be by aspect=true in the [render] section. D-fend probably allows for toggling that in the game's settings. There's also always the option of running the game from ScummVM, instead.

I figured this one out by taking a suggestion I found in a "how to" video about Dosbox.

They said the aspect ratio correction only works if you use the "ddraw" or "OpenGL" render. I went with OpenGL and now the aspect ratio is perfect in fullscreen; black bars on the sides, just like it should be for any 4:3 game being run on a widescreen monitor. Problem solved.

I find it strange that the solution for this is to change the render. Why would this be?