Microsoft's new operating system for x86-based embedded computers became generally available Wednesday at a starting price of $70 per license.

Windows XP Embedded replaces Windows NT 4 Embedded--released in 1999--as Microsoft's operating system for the dedicated-function computers in cash registers, industrial controllers, thin clients, and other devices that run Intel chips and plug into a wall.

The biggest engineering change in XP Embedded: greater componentization of the system software. The new system breaks its functions down into about 10,000 components, which developers can choose to install on devices, compared to about 250 components in NT 4 Embedded. That should let developers preload less code on devices, reducing memory requirements. Building a lightweight operating-system image is key in the embedded-systems market, where disk space, memory, and power consumption are at premiums.

At its Embedded Developers Conference in Las Vegas this week, Microsoft said a minimum system configuration for XP Embedded would take up 4.8 Mbytes of disk space. A basic image built with the Win32 API set and security measures would consume 25 Mbytes of space. And an image built with the full Win32 API set, Internet Explorer, Windows Media player, a terminal server client, and other technologies, takes up about 70 Mbytes of storage.

XP Embedded will also "run in place," meaning it will boot from ROM instead of RAM, boosting performance.

Microsoft argues that embedded developers can build device images using the same calls used by the PC version of Windows. But the company's relatively recent entry into markets such as industrial automation also means embedded Windows lacks the base of independent software developers whose products complement systems from more established vendors.

Licenses for XP Embedded start at $70 per copy, unchanged from NT 4 Embedded. A Windows XP Embedded tool suite features a three-month promotional price of $995.