My laptop won't power on

When I attempt to turn on my laptop, it turns on for a split-second(i.e. lights turn on) and then it cuts right back off. I have already attempted to take out and reinsert the RAM, I have checked the motherboard to make sure that nothing metal is making contact with it(like screws) and I have tried to run it on cord only, battery only and both at the same time. It is a Toshiba Satellite A505 and it is 4-5 years old. Can anyone help me?