[EvilLS1]

In memberlist.php find:

  if ($what=="topposters") {
    $orderby="posts";
    $direction="DESC";
  }

Above it add:

  if ($what=="username") {
    $orderby="username";
    $direction="ASC";
  }

Find:

  if ($orderby=="" or ($orderby!="username" and $orderby!="posts" and $orderby!="joindate" and $orderby!="lastpost")) {
    $what = 'username';
    $orderby="username";
  }

Replace it with:

  if ($orderby=="" or ($orderby!="username" and $orderby!="posts" and $orderby!="joindate" and $orderby!="lastpost")) {
    $what = 'topposters';
    $orderby="posts";
    $direction="DESC";
  }

In your memberlist template find:

	<td bgcolor="{secondaltcolor}"><smallfont><a href="memberlist.php?s=$session[sessionhash]"><b>List Alphabetically</b></a></smallfont></td>

Replace it with:

	<td bgcolor="{secondaltcolor}"><smallfont><a href="memberlist.php?s=$session[sessionhash]&what=username"><b>List Alphabetically</b></a></smallfont></td>