According to research firm NPD Group Inc, which tracks retail sales, Apple Inc - after having outpaced the overall personal computer market this year despite its strategy of eschewing discounts - has showed its first signs of weakness in November.

Last month, sales of Macs in US stores declined 1% from the sales a year ago, while industry-wide PC sales rose 2%. However, Apple's notebook sales were up 22 percent, while Windows sales rose 15 percent. An Apple spokesman said the Cupertino, Calif., company does not comment on monthly sales.

Gene Munster, an analyst at Piper Jaffray, said the data for the month of November indicates that falling prices for Windows-based PCs, and the rise of low-priced computers like netbooks - mini notebooks costing about $300 - have finally tripped Apple. Nevertheless, he still expects Apple to continue outpacing the market over the next year.

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

Apple Chief Executive Steve Jobs told analysts in October the company wasn't cutting prices on Macs - which make up 46% of the company's revenue - because "we're not tremendously worried" the downturn will drive customers to cheaper PCs.

Apple has steered away from the low-margin netbook market, in favor of higher-end computers. When the company reported earnings in October, Jobs said: "We don't know how to make a $500 computer that's not a piece of junk."