According to NPD data Apple grabbed 47.71 percent of U.S. retail desktop revenue during the month of October. The data which comes from Joe Wilcox who spoke to Stephen Baker, NPD’s vice president of industry analysis.

Baker attributed this impressive number down to the release of new iMac models and a decline in PC desktop sales ahead of the October 22nd release of Windows 7.
"Apple gets a huge bump out of new products that no one else gets," Baker said. "Those [share increases] haven't tended to be sustainable in the long term."