Worldwide shipments of PCs fell nearly 12 percent in the third quarter, according to a new report from Gartner Dataquest, with sales in the US declining 18.7 percent. Dell extended its lead as the sales leader, capturing 13.8 percent of the worldwide marketshare and 25 percent of the US market. Apple yesterday revealed that sales during its fiscal fourth quarter, which is roughly equivalent to the calender third quarter, fell 21 percent.