Did you:
1. Remove the battery while it was still plugged in?
2. Reseat the battery after the initial failure?
3. Try it again with the power charger connected?

Can you:
1. Hold down the power button for a lengthy period of time?
2. Connect the tablet to a PC via USB and get any response from the PC?

Does the:
1. Blue LED light on the D-PAD light up at all at any point?

Above all else; be gentle with it. If you just got it today, perhaps you can return it or send it back to Nokia for service.