MacBook will not boot

I know there are a lot of these but here I go. Hello, I have a MacBook Pro model A1226 2.4GHz dual-core. And it will not turn on. But it is weirder than that. So long as you are pressing the power button it will do the normal initial booting sounds fans,cd drive, hard drive, etc. However, as soon as you release the power button, it seems as though all power is cut off from the machine and just stops. This works up until 5 seconds, where then the indicator light flashes quickly several times then it shuts off. I was wondering if either, anyone has encountered this, or if anyone has an idea of what it may be.
P.S. I have recently discovered the computer will not boot without the battery inserted. Nor without the hard drive.

 

Yes I have tried all of these things. I am sure it is a hardware problem. I am really just looking to bounce ideas off you guys about possible causes. Mostly I want to figure out which part to replace so I'm not throwing my money at people.