Install Windows on MacBook

I decided to install Windows XP on (SP3) on my MacBook 13" (early 2007 runing OS X Snow Leopard) with BootCamp 3.0.4, after click on "Start Installation" my Mac restart but he eject my windows CD! I try to holding "C" to force him to boot from CD but it doesn't work! after all I dont what happend!

I had install the Lion on my Mac but I had downgrade it to Snow Leopard! when it has Lion I could install my windows on it but now its impossibel! please help