Macbook Pro chimes then displays a folder with a question mark inside, will not boot to restore disk

I have an older 15" MBP 2.16 GHz Intel Core Duo (model A1150) w/2 GB RAM, which was running OS 10.6.8. I accidentally (like anyone drops their computer on purpose!) let it drop about two feet onto a hardwood floor a couple of days ago. Not sure if that's the root of the problem - but not immediately - more like the next day, it would not boot up normally from sleep or restart. Regardless of WHATEVER I've tried, it still boots to a folder with a question mark inside...

So far I have tried: 1) Resetting the PMU and the PRAM, 2) B/c it was dropped, I took apart the computer to make sure that all the connections, especially to the HDD were fine and all seemed good there, 3) Tried rebooting in 'Safe' mode. No go, same annoying question mark, 4) Tried rebooting from the Snow Leopard disc hoping to use Utilities to repair the disc and/or permissions. No go - it keep spitting out the dang disc! (This also may have to do w/the optical drive which seems a bit dicey - I got this computer from a friend on the cheap and I'm still discovering its "quirks".) I was next going to try to swap Sata HDDs with my Macbook (which I just freshly backed-up for just this purpose) but that's a lot of work and I'm worried that if this is a motherboard issue and NOT an issue with a dead hard drive in the MBP, that I will fry my Macbook's hard drive which would be a very bad thing, obviously...Fyi, like many MBPs this one runs hot and I replaced both fans AND still had to download a freeware program called FMC Fan Control which has been really great in keeping the fans going more or less at top speed to keep this computer cool enough, so I honestly don't think this was a heat issue - but who knows?

Does anyone have any more input/suggestions/help to offer please? Is the motherboard toast?? I've obviously spent Waaaaayyyy too much time on this already, but shucks! I can't afford a new MBP! Thanks in advance to anyone with ANY help!