Sony Vaio SVE151D11M laptop wont start

Hello, a friend gave me his dead laptop to try and fix, I don’t know how it died.

when I press the power button the lights turn on, fan spins for an instant, hard drive tries to start, then everything shuts down and after a few seconds does the same thing over and over.

I’ve tried the reset method removing battery and power and pressing power button for awhile before putting AC back on and nothing.

I try replacing the ram and nothing.

then i realised that if i press power without the ram installed the lights stay on i get fan spin and HDD starts with no problems but there is no image and off course no boot.

Anybody knows what the problem might be?

Thanks.