I'm using the Ultimate Boot CD, and I've added a bunch of customized .iso's to it. I can boot into those .iso files fine, but most of them are mini-versions of Linux that are designed to run off of a CD. When they try to boot, they try to run off the CD (which obviously isn't there since they're on a USB drive) and then either freeze, or don't work in some other way.
Is there any way to edit the .iso files to tell them they're booting off of a USB drive? I'm assuming there'd be something somewhere in the boot configuration files to do this. Where would that be? I would think it'd be different for different ones, but are there some places that are standard for live CDs? What would I have to change?
EDIT: Just to make exactly what I'm asking clear...I know there's stuff all over the place on how to boot a .iso from USB. That's not the problem, I can already do that. What I'm wondering is how to make the OS stored in the .iso realize that it's booting from USB and not CD?