I spent hours looking for a way to access an external USB CD drive at boot from my notebook that does not have a built in CD, but does have USB port.
Took a long time to find it, but this little USB boot disk creation utility is the bomb and will make a DOS USB device boot disk that works for most external USB storage drives. If you’re ever Catch 22’d on OS installs with a system sans a built in CD drive this might help you.
Of course, I’m too chicken to go into DOS much (though I’m getting a tiny bit better), but I know how much I like booting up from a Zip disk or external drive on my Mac. Didn’t know much about how to do it with a PC. I had an old Thinkpad that came with a Parallel port CD drive (because the laptop didn’t have a built-in CD) but I don’t know if it was bootable. Didn’t have the laptop long enough to find out. (Sold it on eBay. I go through laptops like Kleenex.)