Coincidence? I recently had to replace my dead MB and I found that replacement (old ECS K7S5A) has USB booting option in BIOS. Apparently even some older MB's have this capability.
Unfortunately I never got USB memory key working correctly as boot device. It's reckognized as boot device and booting even starts, but process dies shortly after starting. Maybe it's because of USB of MB is v1.1 instead of 2.0? Anyways, USB-HDD is also available.
Erm... can anyone explain what are boot devices BBS-1...BBS-4?