You might want to at least consider the possibility of multiple drives or other volume assignments:

#! perl -slw
use strict;

my @vols = split "\n", `diskpart /s listvol.txt`;

print for @vols;
[download]

Where listvoe.txt contains:

list volume
[download]

Will get you the volume list. You can then grep on /ROM/ and tease the line(s) apart to get the volume number.