MBP doesnt start up when pressing power button

Hy. My MacBookPro doesn't start up when i pressing the power button.

The only feedback i get is the little white led in front of the book will flash up a short time. And a quiet click sound is heard from the harddrive! That's all.

When i hold down the power button for a few secound the white led will go on permanent and i can hear the harddrive spinning on. also the dvd give feedback with his usual start-up-sound. But then the white led starts to flash and the mbp power off. I guess because of the 10sec pressed down the power button.

I have also tested it without batterie and only with AC-Power.

I do a SMC reset ... Nothing changed!

Reseating the memory ... Nothing changed!

When i power on the mbp without memory the white led go on normaly and then i heard a beep. And this beep comes again and again until i pressed the power button for a few secounds.

Has anyone an idea what may be broken or what i can test next?

Thx for the answers!

Mike