Microsoft's MSN Music store shouldn't surprise anybody. The company with its own operating system, online service, digital-music format and media software was always the likeliest suspect to launch an online music store.

But Microsoft didn't rush to open its store last year, when most of its competitors debuted. Instead, it waited until last month -- a delay that allowed it to learn from other stores' mistakes. MSN Music (music.msn.com) is by far the most capable rival to Apple's iTunes Music Store, even if it doesn't yet surpass it.

MSN Music's official launch won't come until Tuesday, an occasion that should bring a flurry of press releases and some new features, but the basics of the store are set. Like other digital-music shops, it charges 99 cents a song and $9.90 an album (save some weirdly priced exceptions, such as Bob Dylan's "Highway 61 Revisited," at $10.89).

Shopping the store is a pleasure, whether in Microsoft's Windows XP-only Windows Media Player 10 or through a Web interface (you can only buy using the Windows version of Internet Explorer). Type what you want into a search form and results are cleanly presented a moment later; each track shown comes with a 30-second sample and a rating, from one to five stars, based on other users' input. This search engine will offer to correct typos, even the most obscure -- it fixed my attempt to spell Einsturzende Neubauten.

Shortcuts to an artist's full catalogue appear to the right. Adjacent "find lyrics" and "find tickets" links, however, issue only generic queries ("U2 lyrics" or "U2 tickets") to Microsoft's MSN Search -- and open Internet Explorer to do this, even if you use another browser.

MSN Music's catalogue includes about 600,000 tracks, up from 500,000 at the start; Microsoft's goal is to pass 1 million. (Apple's store is already there.) The store doesn't claim any exclusives yet, but a "Coming Soon" page lists AC/DC and Radiohead -- both absent from the Napster and iTunes stores.

Purchasing a song requires providing a credit card number and setting up a user account on Microsoft's Passport identity service. Not seeing any clear reason why my Hotmail password (that Web-mail service also requires a Passport login) should unlock my credit card, I set up a different Passport account for this store.

You can buy songs or entire albums in one or two clicks, depending on your choice of settings. Your purchases arrive as Windows Media Audio files, produced at a slightly higher quality level than other stores -- a "variable bit rate" encoding of around 160 kilobits per second that should capture more detail in a song's more complex passages.

The difference in quality was obvious in listening to two versions of Parliament's funk classic "Chocolate City"; an MP3 downloaded off a file-sharing system obscured an entire layer of background percussion that MSN's version had preserved.

But the comparison was much tougher when I auditioned versions of Miles Davis's "So What" purchased off iTunes and MSN Music. In repeated listening, I couldn't pick a clear winner -- although, when played over good speakers, both lacked a tiny bit of the original CD version's depth.

Microsoft's downloads can be played on up to five computers at a time. You can burn any one playlist to at least seven audio CDs before you must rearrange those songs. (Labels can allow a higher limit if they choose; I was able to burn one two-song playlist 11 times before I quit out of boredom.)

You can also transfer each track an unlimited number of times to digital-music players that support Microsoft's Windows Media Audio format and copy-control technology -- i.e., not the iPod. I had no problem moving songs to two Creative Labs players, a Zen Portable Media Center and a MuVo MP3 player.

Moving songs from one computer to the other is far simpler than in the Napster and MusicMatch stores; simply copy the files over, then type your user ID and password the first time you play one of them. You shouldn't have to log in again to play any other downloads moved to that PC, but I had to a few times.

MSN downloads can be played in the MusicMatch and Napster programs, but not the Mac OS X version of Windows Media Player. You can also play downloads in older versions of Windows Media Player, but you lose some usage rights -- the seven-burn limit is absolute, not a minimum, and applies to tracks instead of playlists.

All this is enough to surpass the Wal-Mart, Napster and MusicMatch stores. But MSN's real competition is iTunes -- a benchmark Microsoft doesn't quite meet.

I won't knock MSN for not being iPod-compatible; Apple has chosen not to support other stores' download formats, and there's little Microsoft can do about it. But I will knock MSN Music for not offering the elementary ability to print out CD covers, as iTunes does.

MSN Music is a U.S.-only shop, unlike iTunes, and doesn't offer any gift certificates or purchase allowances, although those are planned for later.

MSN Music also doesn't -- yet -- have any equivalent of Apple's AirPort Express, which lets you play your downloads through your stereo via a simple wireless link. But a family of devices called Media Center Extenders should offer that option later this year.

Lastly, there's this missed opportunity -- none of the CD and DVD players that read Windows Media Audio files off data CDs can play MSN Music downloads.

If you're not going to shop at iTunes, you'd do well to direct your online-music budget toward MSN. But for this store to start winning market share from iTunes, Microsoft has more work to do.

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