Disc won't Load!?

I just got my new Mac OS Leopard in the mail today but for some reason, when I put the disk into my MacBook, it just spits it right back out! I tried three times, then tried restarting my computer to see if that would work, but it still won't load! Does anyone know what I can do? I tried calling the support line a few times but it tells me that no one is available and to call back later, so I figured posting on here might be a better bet! Thanks!