(FORTUNE Magazine) – Windows XP, the new consumer PC operating system scheduled for delivery in late summer or fall, represents a long overdue spring cleaning for Microsoft. The Redmond, Wash., software giant is clearing years of clutter out of the attic of its Windows operating system and moving, in effect, to a modern house with new wiring, in which a few appliances can run at the same time without blowing a fuse.

Microsoft's challenge is to replace the rickety, underlying code base of its legacy consumer operating system (Windows ME, 98, 95, and previous versions) with the more reliable code from its newer NT/2000 system--without substantially changing the user experience. Judging by a recent controlled demonstration in Seattle by Microsoft executives, including chief software architect Bill Gates, it appears that the typical consumer user of Windows XP will get additional power, speed, reliability, and integration without--yes, it's hard to believe--increased complexity.

In an attempt to demonstrate one of the many "innovations" the company says it has built into Windows XP, a Microsoft executive showed a scene from a DVD copy of the film The Fifth Element. Perhaps Microsoft instead should have played a bit from The Princess Bride, in which the swashbuckling Mandy Patinkin says to evil genius Wallace Shawn, "You keep using that word. I do not think it means what you think it means."

Windows XP integrates more than it innovates. But that integration helps: XP takes a mishmash of software packages and drivers from Microsoft and third parties and combines them into a seamless, consistent, and simple interface that's quite attractive and, apparently, fast. (It also seems blessedly free of the wizards and talking office supplies used in previous versions of Windows.)

The most impressive example of integration in the new operating system involves new support for moving digital photographs between the PC and cameras and printers. Microsoft has made working with digital photographs clean, logical, and sensible. However, the new features will require printer and camera manufacturers to write new Windows XP control programs, called drivers, which may not be available when XP is released.

Windows XP also includes direct and seemingly intelligent support for MP3 files and handheld PCs, audio CD "ripping" (converting analog audio to compressed digital files), direct CD writing, hot-swapping for USB and similar devices, video editing, and true support for allowing multiple family members to use the same PC while retaining their own preferences and file systems.

Macintosh users might feel a frisson of deja vu reading that list, as every element is either already integrated into or available in the current Mac OS 9 release, or scheduled for inclusion in the next-generation Mac OS X revamp due out March 24. Microsoft's so-called Luna interface for XP contains some of the 3-D shading found in OS X's new Aqua interface.

A new feature called Remote Assistance, similar to Netopia's Timbuktu Pro, allows a computer-savvy friend, family member, or support technician to remotely grab control of the novice user's computer over the Internet, either to fix problems or, using voice and text chatting, to help the beginner through tasks.

Although many of the features of XP will appeal to inexperienced PC users, Bill Gates asserted that even experts "will want to upgrade the day this comes out, if only for the reliability."

What? Microsoft acknowledging that previous versions of Windows were not completely reliable? Hard to imagine.