Hi, I don't mean to mix up everything here, but I'd like to give some hints.
a) Some flash media can be made bootable by using HP USB Disk Storage Format Tool.
It comes with FreeDOS, but also can ready boot files from physical MS-DOS diskettes.
That tool turns an USB medium, such as a pen drive, into a fake 1.44MB disks, so a modern PC can boot from it.
b) Win32DiskImager can read and write *.IMG files.
It is used for writing back images of SD cards, for example.
One of the popular use cases is the Raspbian OS for the Raspberry Pi computer.
c) In respect of floppy images, *.IMG is just a generic image file extensions.
Some programs also call it *.IMA or *.IMZ (zip compressed).
https://en.wikipedia.org/wiki/IMG_(file_format)
d) Qemu can handle *.IMG files for both diskette images and hard disk images.
Here's an exmple.
[boot.bat]
@echo off
cd files
qemu -L . -m 256 -hda hdd.vmdk -hdb hddb.vmdk -cdrom IsoFile.iso -fda floppy.ima -vga std -serial file:CON
Where -m is memory, -hda is first HDD (supports different formats), -hdb second HDD. -fda is floppy drive A:.
e) Some Compaq machines had their CMOS setup not located in the BIOS' ROM chip.
Instead, the BIOS was installed on a hidden partition of the original HDD.
Alternatively, it was available for download on the Compaq BBSes or FTP servers.
A self-extractor program then would have had written the CMOS utility to a set of bootable diskettes.
f) Your Compaq PC may or may not expect a specific drive geometry. This depends on the BIOS.
If you're facing trouble, you can try to backup the original HDD by using an USB-IDE adapter
and Win32DiskImager on Windows or DD on *nix. The resulting image can then be mounted in an emulator such as Qemu.
Once you installed MS-DOS onto that image, you can write it back to either the original HDD or the CF card (it must the equal or bigger than the image in capacity).
If you choose the CF card, it should accept the image's drive geometry so your Compaq thinks it is the original HDD.
d) If you don't have access to the CMOS program, you can use the default settings and
use one of the old dynamic disk overlay programs (DDOs), such as Ontrack etc.
They work with any drive geometry. However, this may causes trouble if you like to transfer files
between a modern PC, since the LBA algorithm might be different.
e) If you can't or don't want to use a real floppy, get hold of a cheap floppy emulator.
They usually do support the standard 1.44MB format, which is enough for installing DOS or Windows.
OS/2, however, is another story. That would require a more advanced firmware such as FlashFloppy.
Edit: Never mind, just saw it is a laptop computer..
Found a similar thread here: COMPAQ LTE 5280 + DOS + PCMCIA
Maybe the PCMCIA slot can somehow be used ? I recall there were PCMCIA to CF adapters, too.
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