Hi,
I see now that this question is really old and there won't be a point in me answering it. However, in case someone else finds it useful, here it is:
Some laptops end up having a manufacturing defect (the motherboard being bad as you described). This is where your Manufacturing Warranty comes into the picture.
Within a year of purchase, you will be able to hand over your laptop to a nearby authorized service centre (after submitting a support ticket) and have the motherboard replaced Free of Charge.
I faced the same with an HP laptop and all's going well for the past 4 years.
I wish I had seen this question earlier :)