See: http://www.digital-experts.de/doc/mbr/README
- The boot process ~~~~~~~~~~~~~
When the MBR is first loaded it waits for a configurable length of
time (1 second by default), monitoring the keyboard, for key presses.
If the MBR detects a key press, it will interrupt the boot process,
and display it's prompt. Otherwise, it will load the first sector of
the default partition, and execute it. If a disk error occours, the
MBR will display it's prompt.
4.1 The boot prompt ~~~~~~~~~~~~~~~~~~~
The boot prompt looks something like this:
14FA:
This is the list of valid keys which may be pressed. This means that
partitions 1, and 4 can be booted, also the first floppy drive (F).
The 'A' means that 'advanced' mode may be entered, in which any
partition may be booted. The prompt for this mode looks like this:
1234F:
The only other valid key which may be pressed is RETURN, which
continues booting with the default partition.