Macbook won't boot

I have a core duo Macbook that won't boot. When I plug in the magsafe, I get a faint green light. When I press the power button, the white light next to the ir port glows, the screen flickers once and the hard drive spins. The USB ports have power.

I've tried resetting PRAM and SMC, tried command and power together, and held power for 10 seconds...none worked.

Any Ideas on what could fix this? It's out off warranty so I would rather not bring it to Apple

Thanks