"Antoine Leca" wrote:
rdisk(N) is the "real" disk number (as assigned
by the BIOS - 0x80; and up to 3 according to MS doc).


You can also think of "rdisk()" as meaning the
"relative disk position", that is, relative to the head
of the BIOS's hard drive boot order. Since the
boot order can be adjusted manually by the user
via keyboard input to the BIOS, the hard drive
referred to by "rdisk(0)" can be changed at will.
Thus, "rdisk(0)" will refer to the top of the boot
order list, "rdisk(1)" will refer to the next in the list,
"rdisk(2)" will refer to the next after that, etc., but
which hard drive those arguments refer to only
depends on cabling and I/O channel in the default
case.

*TimDaniels*