Int 13 Fn 20  U - Compaq Deskpro/i - Get Current Media Format              [b]

   AH = 20h
   DL = drive number (00h,01h)

Return: CF clear if successful
       AL = media type (see below)
   CF set on error
       AH = error code
       31h no such drive
       32h incorrect drive type stored in CMOS

Note:  this function is supported by the 3/8/93 ROM BIOS, but only partially
     (AL is always 00h when successful) by the 8/3/93 version

Values for media type:
 03h   720K
 04h   1.44M
 06h   2.88M
 0Ch   360K
 0Dh   1.2M
 0Eh   ???
 0Fh   ??? (1024-byte sectors)