Q: HOW do I recover my hard drive after screen has gone? for a 6 year old Mac

It might be a longshot, but since a lot of keys were hit at random the brightness may have just been turned all the way down.  Try the "brightness up" key several times to see if there is any change.

What exactly happens when you try to start up the machine? Nothing at all?

If you can get it to try to start, there are a number of things you can attempt (including, of course, the suggestion above).  For instance, you could boot from your OS installation disk and run Disk Utility, and see if everything is kosher.  You could reset the pram in case something is wrong with the display settings. You could hold down the shift key and start up in "Safe mode" as a key troubleshooting step. If it's just the display, you can hook up an external display. There's more, depending upon what happens.

Resetting your Mac's PRAM and NVRAM

Starting up in Safe Mode

charlie

https://discussions.apple.com/docs/DOC-3172

https://discussions.apple.com/docs/DOC-3046

https://discussions.apple.com/community/notebooks/macbook_pro?view=documents