Dell laptop won't turn on

This is a Dell Inspiron 9100 with XP Home.

Last couple of times it gave a little pop! and emitted a smell of burned electronics, and wouldn't turn on. So the first time I paid to have the motherboard replaced (which is what they said the problem was, although I suspect that isn't the root problem), and got them to replace it again without charging when the problem recurred within a week. This time I shut the laptop, which usually just turns off the screen, and when I opened it again, it wouldn't turn on no matter what. No burning smell this time though. Also if I connect or disconnect the AC adapter (i.e. switch between outlet and battery power) and press the power button, the power indicator light comes on for a few seconds (which tells me that this time the electronics aren't fried), but nothing else comes on.

I've tried shutting and opening the laptop, pressing and holding the power button for a few seconds, and removing and re-inserting the battery, all to no avail.

Please help!

} kenji