if ($username != '' && $_POST['passwrd1'] != '') {  //leave
    $sql_server = "sqlserver_url";          //change
    $sql_server_usr = "sqlserver_username";     //change
    $sql_server_pas = "sqlserver_password";     //change

    $mysql = mysql_connect($sql_server, $sql_server_usr, $sql_server_pas) or die("couldn't connect to server");
    mysql_select_db("sql_database", $mysql) or die("couldn't select the database"); //change
    //change table_name and username_column
    $check = mysql_query('SELECT * FROM table_name WHERE username_column = '."'".$username."'") or die("couldn't check the query");
    $info = mysql_fetch_array($check); //or die("couldn't get the array");

    //leave most of the things below alone
    $sql_str_username = $username;
    $req_password = $_POST['passwrd1'];

    //change table_name, password_column, username_column
    mysql_query('UPDATE table_name SET password_column='."'".$req_password."'"." WHERE username_column='".$username"'");

    mysql_close($mysql) or die("couldn't close server");
};