Need to format Dell N5010. Not able to get in to boot cd launch at the time of system start up

Hi

I need to format my dell N5010 laptop, but my laptop doesn't respond to any of the key presses F8 / F10 / F12 at the time of system start up. Hence every time i try to launch the bootable disc, my system just starts normally and I am not able to get into the window which could enable me to format my laptop.

What should I do now to format my laptop?

Thanks 

Kanika