I used the method, previously described, to make a bootable USB Ubuntu thumb drive for a co-worker. The process failed for his particular thumb drive, saying “Missing Operating System” when he tried to boot with the USB thumb drive. After some research on the subject, it seems that a lot of thumb drives have this problem with Ubuntu. I found the solution at http://ubuntuliving.blogspot.com/2008/11/missing-operating-system-step-by-step.html . Dominique’s step by step “How To” worked perfectly for me. If you have problems with your Ubuntu USB boot thumb drive, give this “How To” a try and you might be pleasantly surprised.