What with all this fiddling around with boot disks and ISO files, I found that there were not many tools around to do *exactly* what I wanted ... namely edit a 2.88Mb bootable floppy image and turn that into a bootable ISO. So I've written IsoCobbler. It doesn't have a GUI, it is command driven, but it suits my purposes. Even though it looks very retro, this is a C# application running on .Net 4. Here is a screenshot of it in action, on Windows 7:
It comes with a default boot image included, and makes it simple for anybody to edit it. You can insert your own zip file called "content.zip" containing a batch file called "start.bat" along with any DOS applications you want. Anything inside "content.zip" will be extracted into a RAM Disk and "start.bat" will be executed when the boot disk runs.
I guess that it might also be useful for creating some sort of emergency boot disk, you could load the zip file with all kinds of tools.
So here is the application (you'll need .Net framework v4 installed and it's best to run it as an administrator) and the source code (Visual Studio 2010). Please drop me a line if you find it useful. If I get time I may fiddle with it some more...
The previous PDP-11 Live CD that I made is great, but it only works with IDE CD-ROM drives, so you cannot use it if you have a SATA or USB CD-ROM. Which is a shame. So I wanted to make a version that doesn't rely on having CD-ROM drivers for DOS, since it's unlikely that I'd be able to support all of the different types of drive. I have tried to get my external USB CD-ROM drive to work under DR-DOS and found that I couldn't make it go.
So, for a few days I have been struggling to create an "El Torito" hard disk image, so that I could make a CD bootable version of a hard disk. I haven't gotten it to work yet. I even tried this (twice actually) by taking the HxD hex editor to an ISO file. I've given up for the time being, but I'll probably come back to it.
However, I can get floppy disk "El Torito" images to work perfectly, including the 2.88 Mb variety. That's how I got the previous Live CD to start (but I was only using a 1.44 Mb image that time). So with a bit of lateral thinking I realised that my PDP-11 disk compresses quite well. So I went off an got an UNZIP program for DOS, from here ... or to be specific, I downloaded unz600x3.exe from: ftp://ftp.info-zip.org/pub/infozip/msdos/.
This means that I can fit DR-DOS into a 2.88 Mb floppy image along with a compressed copy of the PDP-11 emulator and disk. Since everything is inside the 2.88 Mb image, we don't need to load CD-ROM drivers in DOS. It means that this bootable ISO will work with SATA and USB CD-ROM drives, it doesn't need the drivers since it's all done by the BIOS and the magic of El Torito. Cool.