Boot with broken screen

Something really heavy has fallen on my MacBook Pro last week. The result was a broken screen.

After that, I immediately tried to boot, but the superdrive was doing a really bad noise and the boot process hanged. So I removed the Superdrive and I managed to boot the laptop.

I've tried to use the DVI output but it didn't seem to work either, so I used Apple Remote Desktop from an iMac on the network and I managed to use the laptop!! Yeah.

BUT after some successfull boots, it doesn't anymore now. When I press the power button, the fans start, I can hear the HD as well, but no startup sound, and the boot process can't begin. What can I check?

NB: it wouldn't be for a long use, but for a quick backup (waiting for brand new MBP).