Intel Macbook won't start after failing to install Leopard

Hi all,
I finally decided to install leopard on my two year old macbook. The problems came when, after rebooting to start the install, when I was on the menu where you decide on which drive to perform the installation, the computer won't allow me to install it on the harddrive. Saying that that drive needed to be formated in order to work.
I told the computer to stop the installation and reboot from the harddrive, but now is won't do it:
No reboot from harddrive, no reboot from leopard's dvd and no reboot from tiger's dvd.
When I turn on the computer, I see the logo, hear the dvd being access but don't hear the initial chime. After a while, the computer stops trying and turns itself off again.
I cannot go into safe mode as there's no chime.
What can I do??