Your Windows CD should be bootable already. I am presuming your laptop can boot from a USB device. It should be able to detect the USB CD ROM if it was designed for it. Have you tried to see if you can set the CD ROM to be the first device in the boot order? The problem with using a DOS boot disk is that it needs a CD ROM driver on the disk and some changes to the autoexec.bat and config.sys as you suggested. Old MS DOS also needed MSCDEX.EXE as well. You had to tell it what driver to use and what drive letter to assign. This could be a tricky operation. A Windows 98 startup disk had the proper drivers to do this but it's not going to be much help if your OS is XP. Again, have to tried to boot from the CD ROM. That would be the best option.
I have a laptop with an external (USB)cd-rom. I'm trying to re-install Windows.
I CAN boot to my external usb floppy but I can't see the cd-rom.
I could launch my setup if I could access the cd-rom.
Now, I have found lots of info online but it hasn't worked.
Ex: The Duse system.
It tells you what to alter in config and Antoexec but I don't understand where the driver is.
Nothing has work for me yet.
Any clues - Thank you.