Can't download restore CDs unless you can find one on a Torrent site. You can contact the vendor and they can send one to you (you'll probably be chardged for it though).
Usually the second disk is just suplemental programs you may or may not need, can you start the PC without using the second disk? Many programs that are included with a system are not needed or similar ones available for free. Like VLC Media Player to play DVDs, Picassa for picutre sorting/editing, etc....