Something

// delete disabled and inactive user accounts
   $secs = $GLOBALS["INACTIVE_TIMEOUT"] * 86400;
   $dt = sqlesc(get_date_time(time() - $secs));
   $secs = $GLOBALS["DISABLED_TIMEOUT"] * 86400;
   $dit = sqlesc(get_date_time(time() - $secs));
   $maxclass = UC_POWER_USER;

   $res = mysql_query("
   SELECT 
    id 
   FROM 
    users 
   WHERE 
    status='confirmed' 
   AND 
    ((enabled='no' AND class <= $maxclass AND last_access < $dt) 
   OR 
    (enabled='no' AND last_access < $dit))");
     while ($arr = mysql_fetch_assoc($res))