Mac sales zigged as Windows PC sales sagged in Q4 by Philip Elmer-DeWitt @FortuneMagazine January 12, 2012, 11:20 AM EST E-mail Tweet Facebook Google Plus Linkedin Share icons Apple is the only bright spot in the industry’s worst quarter in a decade Source: Gartner. Chart: PED Fourth quarter personal computer numbers for the U.S. market came in from Gartner and IDC Wednesday and for the second quarter in a row, Apple AAPL sales grew like gangbusters while the Microsoft MSFT Windows PC market actually shrank. Apple sales in the U.S. were up 20.7%, according to Gartner, while HP HPQ was down 21.6%, Dell DELL fell 4.5%, Toshiba shrank 2.2% and Asus sagged 11.4%. Next quarter will be even worse for the broader PC market, according to both Gartner and IDC, as the effects of the floods in Thailand and the hard drive shortage fully kick in. UPDATE: Several readers have pointed out that when you back Mac sales out of Gartner’s numbers, the rest of the PC industry actually shrank by 8.6%, not the 5.9% drop shown in the chart.