macbook pro early 2011 won’t restart using the usual forced reboot keys

The screen went black on my early 2011 MacBook Pro without warning. Has happened before but could restart by pressing ‘Enter’ and sign-in screen would appear. This has happened fairly often since I made the mistake to upgrade to 32 bit OS. This time, the keyboard lights were on but went out when I pressed Enter, and the light at the front right came on and stayed on (usually varying brightness while the machine is asleep}. Pressed the power button to force shutdown, which worked. However, on any form of restart try, no startup sound, screen stays black, and the light at the front right comes on and stays on. Hard drive is running but nothing else happens. Tried Shift-Ctrl-Option Power, same result. Tried Command-Option-P-R Power same result. Tried Command-Carl-Power same result.

Have an external HD Time Machine, could not get any reaction via Command-D-Power. Don’t have a Startup DVD.

HELP!!