I have asked myself that question for some time. The background is the need for a flexible boot device for flashing graphic cards. I currently do this with my Shuttle PC. The Shuttle BIOS allows me to boot from USB media. I have prepared a 1 GB stick with the HP formatting tool to run FAT16 with system enabled. I have transferred all DOS files from a Windows98SE floppy disk to the drive and finally put all my ATIFlash files on that stick. It works like a charm in the Shuttle. The snag is the physical size of the Shuttle enclosure. I had to bend the frame of the enclosure to enable fitting two slot cards like the X1900XT. Now the base plates of the coolers start becoming bigger and bigger so that even this will not allow me to fit cards like the 4870 without cutting the corner strut of the enclosure. So I think about transferring the flashing to my Mac Pro. I know that you can do it with CDs and DVDs but it really is an akward process to do this even with CD-RWs. I have run a test with my current USB stick on the Mac Pro but it is not recognized when I push the Alt key on boot. I know that there is a process to boot OS X and Windows from USB Stick. So I need to understand what the differences are. I'm using FAT16 but the other operating systems will use HFS+, FAT32 and NTFS. Is this the only thing that is stopping EFI from recognizing my stick? If the answer is yes, I may figure out a way to run DOS from FAT32? Would that be a solution? If that fails I was thinking about another possible solution. How about partitioning a SATA hard disk with FAT16 (using Partition Magic on a PC) and run DOS from such a boot drive?