RC7: can not boot from USB

[wildcard]

I am having a VERY hard time to get RC7 to boot a PC from a USB drive.  I saw in another thread that PCs that use UEFI are not supported.  Fair enough.  I have an over 12 year old Dell Optima desktop that does not use UEFI for booting.  However, no matter what I try, I can not boot RC7 from a USB drive.  

I do not have any PCs left that can burn the ISO onto a CD-R (the PC with an internal burner is dead and the external CD burner no longer works).  Is there any way to boot RC7 without burning it onto a CD-R?

[grindstone]

Which image are you using? No offense, but the "basics" are ok? (md5 good, boots elsewhere/VM etc)

If you are using CD image, see John's post