Start with the easy stuff.
It is plugged in right?
Have you tried removing the battery while unplugged for a couple of seconds and then putting it back in and then plugging it back in.
After that, check out this article from apple about how to reset pram and nvram.
http://support.apple.com/kb/HT1379
The Stig
Can't reset the PRAM and NVRAM because the computer won't start... now it doesn't do anything at all... I click the power button and nothing..
Did you plug it in? Does the light glow amber indicating charging state?