Hello Manuel!

  MB> You can also hit F5 (or maybe F6 I don't remember) to
    > boot secondary disk. Press enter and it'll boot the
    > default (in your case, the second disk). No need to
    > wait 10s :)

F5 may work, but pressing Enter when the bootselector is
displaying F1: MS-DOS makes it boot DOS.  It's no big deal
really, 10 seconds is a very small proportion of the time it
takes this machine to boot! :-)

Regards,
  - Andy.