Booting from USB drive (SOLVED)

[DavidCooper]

On further reflection, I think you're right - using extra sectors does have the edge. I doubt there are any flash drives or hard drives that don't have plenty of free sectors available, though on an internal drive some of them may already be used for storing spare copies of the MBR, and be aware too that GPT uses extra sectors outside of the partition, so you don't want your loader to conflict with those. The space immediately following the VBR is probably the best bet for placing your loader, and you could store a copy of the original VBR there too so that it can be restored later if necessary.

(I wasn't suggesting that a machine's behaviour is awkward if it refuses to do anything other than unhibernate - that's probably a good thing as you may have forgotten that you left something important open without saving data. What I was trying to suggest was that there may be some kind of bug where something is accidentally set that blocks the machine from booting via USB - it seems unlikely to be an intentional barrier unless something like secure boot is in place because it makes recovery harder if the OS gets corrupted.)

One more thing: it might be worth trying to boot from a USB hard drive, just in case the BIOS treats that differently from a flash drive. That probably won't help, but it would be interesting to know what the limits are.