Windows XP lost 2.4 percentage points of share to post a December average of 46.5%, a new low for the aged OS in the tracking of Web metrics firm Net Applications. The month's fall nearly matched the record 2.5-point drop of October.

In the four months from September to December, XP jettisoned more than 11% of its share as of Sept. 1, falling by nearly six percentage points during the period.