Microsoft's Windows Media Player has grown from a forgotten item in the "Accessories" branch of Windows 95's Start menu to one of Windows XP's flagship applications -- and a core part of the company's strategy to make its products as essential in audio and video as they are on personal computers.

The latest version of this software, Windows Media Player 9 Series, shipped two Tuesdays ago. It's really two updates in one; your download (9.7 megabytes for Windows XP; 13.3MB for Win 98 SE, Millennium Edition or 2000) gets you an updated application and a set of new file formats.

The program's install is pain- and restart-free, with a refreshingly clear explanation of your privacy options and no sneaky attempts to spam you with marketing pop-ups. Other media-software developers -- yes, RealNetworks, that means you -- could learn from this.

Unfortunately, the new Windows Media Player hasn't improved on its predecessor's inefficient, designed-by-committee looks. Its navigation bar mixes Web links (Media Guide, Premium Services), tasks (Copy From CD, Copy to CD or Device), file browsing (Media Library) and alternative interfaces (Skin Chooser) in no clear order, sometimes scattering related functions into segregated screens. A menu bar that hides automatically every now and then eliminates access to the Options window, and the relocated button for shuffling tracks looks like the old WMP's graphic-equalizer button.

Some of WMP 9's alternative skins are quite elegant and artistic; Windows XP users can also collapse the interface to a "Mini-Player" task bar module. But these replacements are no substitute for getting the defaults right.

The music-management interface remains an awkward two-pane layout, reminiscent of Windows Explorer, that hides some convenient features behind right-click menus. In its favor, WMP 9 adds an auto-playlist feature that generates song sets on the fly based on your listening habits and other criteria, plus an expanded set of listening options -- computer-generated visualizations of songs, additional controls and sound-effects plug-ins. Unfortunately, I could not get the reverse-playback feature to work, so I still don't know if there are any hidden satanic messages in my CD collection.

A Radio Tuner screen is simple but spotty in its coverage. Selecting a Web radio station opens its home page in your Web browser. That's both intrusive (what if I were browsing elsewhere?) and unhelpful (how about putting the station's info in WMP's own window instead?).

Pop a CD into your computer and Windows Media Player will reach out to a Web database to compile a (usually accurate) dossier on the disc -- not just artist and title, but also cover art, a bio of the artist, news headlines and links to related music. WMP 9 will also fill in missing information in your music library and even adjust volume settings so each file plays around the same level.

When you first copy music to your hard drive, Windows Media Player will ask if you want to copy-protect it. You can't select "no" and move on until you click an "I accept" check box next to a vague scolding about copyright restrictions.

There's no good reason to opt for copy protection. It restricts you to 10 copies of the song and requires that each copy be activated by visiting a Microsoft Web page. Windows PCs took me to that site automatically, but the Mac OS X version of Windows Media Player only yielded an "unknown error" message when presented with a copy-protected song.

WMP 9 introduces a couple of new song-recording options, and here's where you get the second, better part of this update -- new "variable bit rate" and "lossless" Windows Media formats.

The former improves sound quality by varying compression rates to suit the music's complexity, while the latter -- available only in Windows XP and requiring 300MB or so per CD -- is intended for audiophile and archival use. Both are excellent additions to Microsoft's format.

The player still won't save a song as an MP3. Microsoft says its formats sound better and don't require it to pay a licensing fee. The trade-off is less flexibility in moving your music: Not all portable music players support Windows Media Audio, and of the CD and DVD players that play digital music files on data CDs, most only support MP3.

Comparing these encoding formats gets tricky -- over cheap headphones, they all sound pretty close to each other. In better listening conditions, the medium-low variable-bit-rate WMA setting dulled the thunder of the first movement of Beethoven's Third Symphony and sucked some air out of the dense soundscapes on alt-country band Wilco's "Yankee Hotel Foxtrot" album.

The medium variable-bit-rate option, however, noticeably sharpened the audio quality, as if somebody had wiped a layer of dust off the notes. The results sounded fractionally clearer than a 128-kbps variable-bit-rate MP3 encoding while taking up fractionally more space.

WMP 9 also introduces improved video compression, but the videos I've seen online (at rates as high as 300 kbps) look as grainy as other formats. The biggest improvements only seem to come at faster-than-broadband speeds.

You can expect to see more of both Windows Media audio and video, and not just in computers. Microsoft has been lobbying entertainment and electronics firms to adopt its formats for such uses as high-definition DVDs, camcorder recording and music distribution, both online and on copy-protected CDs.

The scope of these ambitions makes me queasy. Microsoft has not wielded market power responsibly in the past, but even if it were run by angels, would you want any one company to be so essential to so many parts of the economy?

Living with technology, or trying to? E-mail Rob Pegoraro at rob@twp.com.