use strict; 
my $drive;
my $count = -1;
open( LIST, "tpconfig -l|" ) or die $!;
while( <LIST> ) # I added the <LIST>... which I suspect you had.
{
    ($drive) = unpack '@0 A8',$_;
    ++$count if m/^drive/;
    system("tpconfig -delete -drive -index ${count}");
    # You should check all system calls for error.
    # system will set $? to an error code for you.
}

##</code><code>##

system("tpconfig -delete -drive -index ${count} 2>nul:");
die "Unknown Error with tpconfig $count" if $? >> 8;