By Aidan Malley

Published: 07:20 PM EST

Although Microsoft's opening keynote at the Consumer Electronics Show outed record-setting Windows Vista sales figures, supplemental information suggests the software's debut may have been underwhelming in a larger context.

While outgoing company chief Bill Gates' announcement of Vista sales surpassing the 100 million benchmark was accurate, it doesn't tell the whole story, Electronista says in its analysis of the figures.

Citing Gartner Dataquest information, the report reveals that worldwide PC sales should tally up to about 255.7 million computers over the 12-month period, leaving Vista at just 39 percent of all new sales.

And as Windows XP was Microsoft's primary operating system until Vista's late January 2007 debut, the information suggests that the older OS has sold more copies over the course of the past year than its newer, more heavily promoted replacement -- by a margin of 50 percent or more, the article notes.

The CES update also provides an opportunity to dissect the Windows creator's sales numbers. Microsoft was initially quick to report that its Vista sales rate more than doubled XP's, selling about 20 million copies in one month. In the following months, however, initial enthusiasm for the OS has reportedly petered out, slowing down over the year to where only 12 million units of the Windows update were sold in the fall 2007 quarter.

Microsoft's sales figure, while the best ever for a Windows release, also belies the change in market conditions. While Vista's 100 million mark bests Windows XP's 89 million, the PC market has doubled in size since the earlier version's October 2001 launch, indicating that Vista accounts for a considerably smaller portion of the market than XP did in the past.

The discrepancy is chalked up primarily to a lack of enthusiasm about the OS. Some PC vendors, most notably Dell, brought XP back as an option after customers complained about having to buy new systems with Vista pre-installed.

Apple has taken advantage of this reaction in its Get a Mac ads, claiming that users are "giving up" on Vista in favor of XP.