Windows XP outsold Windows Vista at retail outlets by approximately 60% in the first week of commercial availability. According to research firm NPD, boxed copies of Windows Vista haven't exactly been flying off the shelves and sales trailed at a distance in comparison to those of Windows XP. Microsoft has invested in excess of $500 million in the marketing campaign for Windows Vista, while Windows XP only has $200 million, but failed to tip the balance in Vista's favor.

NPD revealed that Vista retail sales are 58.9% lower than those of XP. The weaker Vista sales are in correlation with lower revenue. According to NPD, Windows Vista revenue was also down 32.1% from XP's performance back in 2001. The only aspect where Windows Vista managed to outperform XP was in PC sales. In the first week of availability, sales of machines preloaded with Windows Vista outperformed sales of XP-based PCs by 67%.

Microsoft managed to sell an estimated 300,000 copies of Windows XP in the operating system's launch week. In the first week they hit the shelves, Windows 98 was sold in over 400,000 copies. Some 25,000 copies of Windows Vista have been sold every day for a forecasted total of 125,000 in the first week. That is less than even Windows 2000 that scratched the 200,000 units sold milestone. In this context, Vista sales are affected by the operating system's hardware requirements.

"All the reviewers have been beating people over the head about hardware requirements," commented Chris Swenson, NPD's director of Software Industry Analysis. "The preliminary data suggests that consumers are getting the message that they need a more robust system to take advantage of some of the new features in Vista. So, although total dollars were down compared to XP, I think the preliminary data shows that Microsoft's gamble on a new high-end Vista SKU will help keep dollar volumes from declining as rapidly as unit volumes in the near term."