According to a software-tracking firm, Windows XP is selling well at retail, but not at the pace of Windows 98, the best-selling version of Windows. Analysts at NPD Techworld said this week that XP's lower sales are probably related to the weak economy and high sales of XP-based PCs, which aren't included in the retail sales figures. XP-based PCs were widely available a month before XP's October 25 launch.

"Just taking a look at the numbers, it's not selling as well as \[Windows\] 98," said senior NPD analyst Steve Koenig. "The volume isn't there." NPD noted that XP sold 400,000 copies at retail in October, but just 250,000 in November. These numbers compare to 580,000 copies of Win98 sold in its first month of availability and 350,000 in its second.

But retail sales aren't necessarily an important measure of success because they represent less than 10 percent of XP's overall sales. Most copies of XP are sold with new PCs, and PC sales have been higher than expected this quarter. Based on NPD's figures and an earlier Microsoft announcement, manufacturers sold more than 6.5 million copies of XP with new PCs by the end of the first week of November. Microsoft says these numbers make XP the best-selling Windows release ever. Chairman and Chief Software Architect Bill Gates noted in his Comdex keynote speech in November that XP sales were "more than double" that of any previous Windows release.