Can't boot from new hard drive

[A J Annala <a.annala@ucl.ac.uk>]

>I purchased a new 1.3gig Toshiba hard drive, and have installed it
>in my ThinkPad 755CX, but I can't boot off of it.
>What do I have to do to get the ThinkPad to boot this new hard
>drive?

I had the same problem on my old IBM PS/2 Note N51/sx (386SX-16, 2MB,
40MB) system.  The drive passed diagnostics.  It just wouldn't boot.

This seems to be a common DOS problem on notebooks.  I've never seen
anyone have the same problem on desktop systems.  There is what seems
to be an undocumented flag on FORMAT, FDISK, or SYS -- /WMB -- which
means something like Write Master Boot (block).  You probably need to
run this command to boot from your hard drive.

Neither one of the following two paragraphs apply to your system:

  Also, there may be an issue with the geometry of your drive.  Some BIOS
  (I'm not sure about your BIOS) do not like to boot from an image which
  is stored on a hard drive above the 1024th cylinder.  You can get around
  this problem by making two partitions -- and keeping the bootable image
  of DOS in the first partition -- below the 1024th cylinder.

  If you had a TP750, 750C, 750Ce, 750Cs, or 750P with the original BIOS
  you might need to install the new system program service diskette --
  SYTPS141 available from http://www.pc.ibm.com/pub/mobiles -- the V1.05
  update of the system program enabled access to disk drive >= 512MB.

Does anyone know why the /WMB flag (or whatever it is) is undocumented?
I have to work from vague ancient memories to answer this question.