Nvidia shares dropped significantly on news of lower sales, with the double whammy of a estimated $200 million charge to replace defective laptop chips. Nvidia was already struggling to compete with AMD’s subsidiary ATI, plus an encroachment on Nvidia’s bread and butter graphics processors by industry leader Intel. A soft economy isn’t helping much, either. The warranty cost for the chips is especially galling; Nvidia says the chips were OK but were damaged by their packaging material. Ouch. In the past six