Nearly two months after the launch of what Microsoft called one of its most important products ever, the Windows XP operating system has failed to sell more copies than its predecessor did in the same period after its release.

Since its 25 October launch, Windows XP has sold around 650,000 copies through retail channels, as opposed to roughly 900,000 copies of Windows 98 sold in the two months after it was launched, according to Howard Dyckovsky, vice president of software tracking at market research firm NPDTechworld.

Windows XP tallied sales of around 400,000 copies in October and 250,000 in November, he said.

With luck readers of and others will have heeded our words about the bizarre pricing differences in play in retail channels.

Though the numbers may appear disappointing, Dyckovsky says they're not.

"Given the market conditions, sales are pretty good," he said, adding that "[XP] will end up selling more than 98 and 95 did, but it will take a while. Overall, it will clearly be the biggest selling operating system that Microsoft has."

The dip Windows XP has taken compared to Windows 98 can be explained by a number of factors, said Dyckovsky.

The state of the economy and the low price of new computers may be either keeping users from upgrading immediately or is causing them to buy new PCs with Windows XP preloaded, thus taking sales figures away from the retail charts.

PC makers were also able to sell PCs with Windows XP in advance of its launch, which may have also hurt retail numbers.

Though Windows XP is not taking the world by storm, Dyckovsky expects that this year's sales likely line up with Microsoft's expectations.