SAN FRANCISCO (AP) -- Microsoft Corp. co-founder Bill Gates hopes to wow a technical conference Tuesday by showing off a prototype of a new personal computer, but he won't spend much time detailing its processor speed, memory, or other hardware and software minutiae.

Instead, he'll point out simple features like how the PC stops playing music when an attached telephone is picked up, or how lights built into the monitor frame alert users to an urgent E-mail or voice mail even with the display dark.

The demonstration will focus on usability and user friendliness--something that has often escaped the computer industry as hardware companies build machines and separate programmers come up with the software to run them.

The prototype machine, code-named Athens, had its hardware and software jointly built by Microsoft and computer giant Hewlett-Packard Co. With a built-in Internet telephone and video camera, it's targeted at businesses and improving worker productivity.

"It's more than just slamming things together," said Steve Kaneko, design director of Microsoft's Windows Hardware Experience Group.

The prototype is to be unveiled at Microsoft's Windows Hardware Engineering Conference, which starts Tuesday in New Orleans. The company also is expected to reveal details of its controversial attempt to bolster security through a combination of hardware and software changes in its next Windows version, code-named Longhorn.

Joe Peterson, general manager of the Windows User Experience Team at Microsoft, said past development in personal computing has suffered because hardware and software makers design their products "in silos."

"We think we can take that innovation and bring it together at a deeper level than we have in the past," he said.

Athens is a continuation of a strategy Microsoft has embarked on in recent months with the development of versions of the Windows XP operating system built specifically to take advantage of hardware in tablet PCs or entertainment center computers.

But Athens, executives say, goes even further, adding seemingly common sense features that have escaped computer manufacturers.

To log onto the machine, the user simply inserts a special plug into the side of the screen and touches a fingerprint reader. The keyboard and mouse are not only wireless but also charge their batteries when docked to the monitor.

In the frame around the display, lights indicate whether messages await the user. Those are lit even when the monitor is in screen-saver mode. It would alert users when they first enter their cubicles, Kaneko said.

"We're extending the Windows experience beyond just the screen," he said. "You're starting to see these things move out into the physical environment."

In an improvement that has been built into some computers already, devices most commonly accessed by users--the CD-ROM drive and Universal Serial Bus ports--are built into the display. The central processing unit case, meanwhile, shrinks.

If a user is listening to music and the Internet phone rings, the tunes stop playing when the handset is lifted. The music starts again once the call is complete.

In videoconferencing, the window showing the other party is displayed adjacent the camera, so that the user appears to be looking the other person in the eye.

"It's a small example but a powerful one of software and hardware working together to address a problem that's fundamentally just not right yet," Kaneko said.

As a prototype, Athens won't appear on store shelves, though HP and Microsoft said elements of its design could start appearing in business computers as soon as the end of this year.

Microsoft makes hardware including as Xbox gaming consoles, mice and keyboards and has been working more closely with hardware manufacturers of late. But company executives say they have no plans to become a personal computer maker.