Acer has officially leapfrogged Dell to become the world's second-largest PC builder, iSuppli confirmed in a new study. The Taiwan firm's computer shipments jumped 16.6 percent year-over-year in the summer to nearly 10.74 million PCs, or a 13.4 percent share of the entire market. Meanwhile, Dell actually dropped 5.9 percent to ship 10.34 million PCs, or 12.9 percent of the whole group.