One in four Macs now run OS X Mountain Lion, Apple's newest operating system, data released last week showed.
But there are signs that OS X Snow Leopard, an edition shipped in August 2009, may be the Mac's equivalent of Microsoft's Windows XP, an OS that stubbornly refuses to go away.
Mountain Lion, also known as OS X 10.8, accounted for 25.8% of all Mac operating systems during October, according to statistics from metrics company Net Applications. That represented a three-and-a-half-point increase over September.
Apple issued Mountain Lion on July 25.