HELP, my Inspiron 600M is dead

I own a Dell Inspiron 600M (P m 1.6Ghz, 512MB, ATI 9000 w/ 64MB)

I don't usually use it much, but here's the story, the unit was still working fine a few hours ago when I first turned it on to check my emails in the morning. I think I used it for around 5 minutes.

And then just a few minutes ago in the afternoon, I copied some files under DOS mode, I then shut the notebook off. Then thinking I am not quite done yet, I tried to turn on the notebook again.

I pressed the round power button and to my surprise, the notebook won't turn on!
The 600M seemed to be dead. Upon a closer look, I noticed the one of the LEDs near the bottom right of the LCD display were on. To be specific, the third on from the left, it has the icon Battery, blinked an orange LED for a fraction of a second when I pressed the power button. THE END. Nothing else happened, no fans, no displays, etc.

I then took a look at the adaptor, I did observe something interesting, when I connect the adaptor to the power socket, BUT NOT to the notebook yet, the green LED on the adaptor lights up. However, as I connected the adaptor to the notebook, the LED is gone. And as said above, there's this quick orange blink in the battery indicator.

I then disconnected the adaptor. I have the battery pack, and I confirmed the battery pack has power. (It was at the fifth level) so I tried to turn on the unit with only the battery pack. Nope, same orange blink.

What is happening? a few seconds ago it was all fine, and now the thing is completely dead.

What should I do!!! HELP!!!

Tried everything, tried it with only the adapter, only the battery,and both adaptor and battery. It all ends up with the orange blink.

The battery still holds a good charge.

I've asked someone else and they're saying the motherboard is busted and an replacement is necessary. Can anyone vouch for this?

Thanks!!!