Man, Ben's gonna have a field day with my Perl...

#!/usr/bin/perl -w

use strict;
use Win32;
use Win32::NetAdmin;

my $domain;

$domain = Win32::DomainName();

my $pdc = "";
my $rc = Win32::NetAdmin::GetDomainController("",$domain, $pdc);

print "Processing user list from $pdc in $domain\\n";

my %users;

%users = Win32::NetAdmin::GetUsers($pdc, FILTER_NORMAL_ACCOUNT, \\%users) || die "GetUsers() failed :$^E";

foreach (keys %users) {
  print "Checking group memberships for $_\\n";
  if (Win32::NetAdmin::GroupIsMember($pdc, "Domain Users", $_)) {
    print "$_\\n";
  }
}

sub PrintIfGroupMember($p, $u, $g)
  {
    if (Win32::NetAdmin::GroupIsMember($p, $g, $u)) {
      print "$u is a member of $g\\n";
    }
  }