code that merely emits an error and waits for a key press before
rebooting. The error being that extended partitions are not
bootable. The origin is presumed to be Windows 2000; Windows XP
does not do this...
For now, ignore the first 96 bytes when checking that the EBR is
(for the most part) all zeroes.
Tested by: Mario Lobo <mlobo@digiart.art.br>
MFC after: 1 week