if it said "sold as is"... then it HAS to be accepted "as is".... if he reviewed you positive and two months later he backs out... what do you think.... the motherboard was good, now he "fried" it he wants a refund.... while it said as is... he might´ve well thought it MAY have had roasted soon after purchase, but that´s a chance he was willing to take when he bought it... even if it was in great condition...

it´s like when buying a light bulb... you check it at tha store and it works fine.... you get home and install it.... and boom... it fuses... you get no refunds...

I really don´t see why you should refund him... I know it must be annoying to get his emails, but ebay must see it as it is.... don´t let it get to you