Sorry to say, but this thing sounds like it's toast. At first I was hopeful there might be a small glimmer of hope in that it was one of the nVidia boards that you might have a shot at getting replaced free, but every time I've seen what you're describing, it's been new MLB to fix.
Still, you can hope you'll get lucky, and try each RAM module individually in each memory bank. There's always a possibility of the RAM having gone bad, and while it's a very distant hope, it's about all you've got at this point.
Since you don't have a whole lot to lose, you could probably take a look at the iFixit site for a guide on taking the thing apart. You could try disconnecting some of the internal bits and bobs, though there's really not much to disconnect on those besides the ODD and some sensor cables once the top case is off.
As long as there's no liquid damage or anything like that, the unit should be eligible for Apple's flat rate repair service. About $300, give or take, and they'll fix pretty much anything that's wrong. There are a few little catches, but barring liquid damage or drop damage, it's pretty unlikely you'll run into those. Apple's depot isn't actually run by Apple, it's a company called Flextronics, but they are required to meet Apple's standards. Like any place, sometimes your unit gets worked on by someone who's pretty green, but they have to warrant every unit for like 90 days, so you can at least get it fixed again for free.
I have a 13 inch Macbook Pro, circa 2008, one of the 2GB Memory/250 GB HD, silver keyboard ones.
It has worked beautifully for me for the last 4 years, but recently I had my first (major) issue.
In the interest of full disclosure, my Magsafe adapter has seen better days, and my battery was at "Replace Now" status for some time. Coconut Battery had it at 20% of original capacity when I checked it about a week ago.
I used the Macbook on Wednesday evening with no issues, I closed the lid (I never put it in Sleep Mode or shut it down) like I always do, but when I opened up the next morning, it would not boot up.
By which I mean, I open the lid, the optical drive makes its normal twitching sound, but instead of the display coming on, nothing. I held down the power button and it turns off, and I can press the power button and it powers on (CD drive makes noise and fans turn on, light below trackpad also comes on), but the computer doesn't book up, there is no "chime" sound, and nothing on the screen. I hear no activity, other than the fans slowly whirring. The caps lock button does not light up when pressed, and neither does the Apple logo on the lid.
Thinking the battery was bad, I took it out and attempted to boot with just the MagSafe plugged in, with the same results..nothing. The battery will charge, but the computer just won't boot up.
In addition, if I leave the computer "on" (in this semi on mode), the CPU area on the bottom gets very hot, even if the lid is closed, even if it's turned upside down to let the bottom "breathe".
I have ordered a new battery, thinking that may be the issue. I've tried to reset the SMC (take out battery, hold down power button for 5 seconds, replace battery), with no change.
Since the computer is 4 years old, I don't have AppleCare or the luxury of taking it in for service without paying. I was hoping someone here could advise on a (hopefully) simple solution, or just tell me what could be wrong. Again, it was working fine one night, and then 8 hours later would not boot.
Thank you in advance.