OS discs? The machine should have come with backup DVD or CD's
I haven't seen PCs come with backup discs for a while now. Most PCs now come with an extra partition, a restore partition. It works well, if the HD isn't fried. You have the choice to make restore DVD's from the partition when you first start the machine up, or at a later date manually, most people don't. You can also order them, for a fee of course.
BTW your machine should have a windows sticker on the side or somewhere else with the windows license number. You can ask a neighbor if they have a disk (XP I'm assuming?) and restore it with that, just use your license number to activate.