[Admin]

Try this:

$checkuser = $DB_site->query_first("
	SELECT userid,username FROM user
	WHERE usergroupid = 14 AND
	(username = '".addslashes(htmlspecialchars($username))."' OR username = '".addslashes(eregi_replace("[^A-Za-z0-9]","",$username))."')
");
if ($checkuser) {
	$DB_site->query("UPDATE post SET username='".addslashes($checkuser['username'])."',userid=0 WHERE userid='$checkuser[userid]'");
	$DB_site->query("DELETE FROM user WHERE userid='$checkuser[userid]'");
	$DB_site->query("DELETE FROM userfield WHERE userid='$checkuser[userid]'");
	$DB_site->query("DELETE FROM access WHERE userid='$checkuser[userid]'");
	$DB_site->query("DELETE FROM calendar_events WHERE userid='$checkuser[userid]'");
	$DB_site->query("DELETE FROM customavatar WHERE userid='$checkuser[userid]'");
	$DB_site->query("DELETE FROM moderator WHERE userid='$checkuser[userid]'");
	$DB_site->query("DELETE FROM privatemessage WHERE userid='$checkuser[userid]'");
	$DB_site->query("DELETE FROM subscribeforum WHERE userid='$checkuser[userid]'");
	$DB_site->query("DELETE FROM subscribethread WHERE userid='$checkuser[userid]'");
	$DB_site->query("DELETE FROM session WHERE userid='$checkuser[userid]'");
}