Sales of personal computers slid for the sixth consecutive quarter at the start of 2016, falling to levels not seen since 2007, a market tracker said Monday.A survey by research firm Gartner shows a 9.6 percent drop in PC sales in the first quarter compared with a year earlier, to 64.7 million units. Figures released later in the day by International Data Corporation (IDC) indicated an even steeper slide, with PC shipments in the first quarter of 2016 down 11.5 percent year-over-year to 60.6 million units.Analysts had anticipated a relatively weak environment for PC sales during the first half of this year as businesses are still testing switching to machines powered by the latest Windows 10 software and the consumer market remains cobbled by volatility in stocks, commodities and currencies, IDC said.