DOS 7.1 or later is required to access FAT32 partitions.
DOS\FreeDOS cannot access NTFS partitions unless a special NTFS driver is added.
Files with long file names (longer than 8.3) may not be listed correctly unless you load a LFN driver. Use 8.3 conventional short filenames with no spaces.
See here for more info on limitations of versions of DOS.
Using a .imgPTN file
An easy way to make and modify your own DOS-bootable image is to create a FAT32 .imgPTN file.
This allows direct access to the DOS files without needing to make a .ima or .img file.
1. Find a suitable MS-DOS 7 or 8 or FreeDOS floppy disk image or zip file or set of DOS boot files.
2. Extract/copy the files to an empty new folder (e.g. .\MyDos) on your Windows Desktop.
3. Drag-and-drop the new folder (MyDos) onto the MPI_FAT32 Desktop shortcut (you must install the MPI Tool Kit first).
4. Copy the 38MB .imgPTN file that this makes to your E2B drives \_ISO\DOS folder.
5. Run \MAKE_THIS_DRIVE_CONTIGUOUS.cmd from the E2B drive.
6. Now either MBR-boot to E2B and select the new .imgPTN file or use \_ISO\SWITCH_E2B.exe to switch it in.
7. The E2B USB drive will now appear as a 38MB FAT32 volume. You can directly change the files on it or edit any of the files.
You can test it by using RMPrepUSB - F11 (QEMU) to boot to it (or use Virtual Box+VMUB).
To restore the E2B drive, run \e2b\SWITCH_E2B.exe - Restore E2B Partition(s), or MBR boot from the USB drive and select menu item 0.
Tip: name the file with a .imgPTNAUTO file extension to avoid the 'OK to switch' user prompt.