And in the spirit of TIMTOWTDI, here's my take using OLE and the Windows Scripting FileSystemObject.

It'll find the total size of the folder very quickly (useful by itself), then iterates through the files. Error handling not included ;)

#!perl -l
use warnings;
use strict;
use Win32::OLE qw/in/;

die "Usage: $0 [dir]" unless (!@ARGV || -d $ARGV[0]);

my $fs = Win32::OLE->CreateObject('Scripting.FileSystemObject');
my ($count, $maxname);
my $max = 0;
my $dir = shift || 'c:/temp';

my $fold = $fs->GetFolder($dir);

print $fold->Size(), " total bytes used";
folders( $dir );
print "$count total files, $maxname = $max";

sub folders {
    my $dir = shift;
    my $fold = $fs->GetFolder( $dir );
    foreach my $file ( in $fold->Files ) {
        my $size = $file->Size();
        if ( $size > $max ) {
            $max = $size;
            $maxname = $file->Name;
        }
        $count++;
    }
    foreach my $subdir ( in $fold->SubFolders ) {
        folders( $subdir );
    }
}
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