function open_pc1() {
  window.open ("pc1_book.php", "book_window","location=0,status=0,scrollbars=0,width=510,height=590"); 
}

function open_pc2() {
  window.open ("pc2_book.php", "book_window","location=0,status=0,scrollbars=0,width=510,height=590"); 
}