age of machine & who's' HD & OS &what is/was installed on machine.
Can you boot to safe mode or that option group, I'm hoping "last good config" still exists & could be used.

Can you hear your HD spinning up when you try to boot (or just clicking sounds or other noise)?? If you open & close (by pushing buttons) can you hear/tell if CDROM or DVD is trying to start up??

I Fear HD or even DVD May be problem source. Hopes go w/ you! Happy