Apple Inc witnessed flat year-over-year overall sales in the United States for its Macs in November, while sales of rival Microsoft Corp's Windows PCs were up 7%, according to research firm NPD Group Inc, which tracks retail sales.

Sales of desktops were down 20% overall, with Windows desktops sales falling 15% and Macs down 38%.

Apple's notebook sales, however, were up 22% in November, while Windows sales rose 15%.

"For notebooks, there is a little extra value to consumers [to buy Apple]. For desktops I'm not so sure," NPD analyst Stephen Barker told Reuters. "To me the real story is the iMacs need a refresh."

IDC, which tracks sales of technology products, said earlier this month that it expects global PC sales to fall 5.3% next year to $267 billion.

Apple and Microsoft could not be immediately reached for comment.