It looks like you might be dealing with a corrupted BIOS. Just make sure you've run through your usual troubleshooting steps first to rule out anything else before diving into this.
If you're still stuck, here is how you handle the recovery:
1. Shut down the computer that has the black screen.
2. Use a different computer to grab the right Driver Pack : Dell Latitude 650 from a USB drive:
Dell Latitude 650 :- sp70256.exe (43 MB)
http://h20564.www2.hp.com/hpsc/swd/p...1&swEnvOid=405...
Quick heads-up: there might be a newer version of this software out there. It’s worth checking for an update at
http://www.hp.com/3. Hit OK.
4. Choose the option to "Create a USB flash drive to update or recover the system BIOS on another Dell Personal Computer." Click Next, pick your flash drive, hit Next again, and then click Finish.
5. Plug that USB drive into the computer with the black screen.
6. Hold down the Command Key + b and the power button at the same time.
7. Let go of both once you see the screen's backlight flash.
Just a note: the machine starts the recovery automatically once it powers up, even if the screen stays dark. You'll know it's working because the Caps Lock LED will be blinking.
8. Once you see the message "A System BIOS Recovery has occurred. BIOS Recovery (500)," go ahead and restart the computer.