Apple's growth was attributed to improved availability of the new all-in-one iMac desktop by analyst Gene Munster of Piper Jaffray. NPD's research tracks sales of computers sold domestically.
The data shows Mac sales continue to grow through the March quarter, albeit at a slower pace than the major 31 percent spike in U.S. Mac sales Apple saw in the month of January.
Munster's forecasts still call for total global Mac sales for the March quarter to be down 5 percent year over year, though he admitted there is room for "some slight upside," given the latest sales estimates. He projects that Apple will sell 3.8 million Macs in the three-month span.
iMac sales were down 700,000 units year over year in the December quarter as Apple faced apparent issues with production due to a new screen lamination process. Limited iMac availability was the chief reason cited by Apple officials for a 17 percent drop in Mac sales in the December quarter.
In all, Mac sales fell 800,000 from holiday 2011 to a year later, from 4.9 million to 4.1 million. Apple's struggles ended a long-running streak where the Mac had continued to outgrow ? or in some cases shrink less than ? the greater PC market.
Finally, the NPD's data also found domestic iPod sales were down 16 percent year over year in the months of January and February. Munster has predicted that iPods will be down 17 percent worldwide for the full quarter.