The portable MP3 player has changed the way people listen to and use music. Technological innovations, both in hardware and software, keep the field fresh and exciting — and sometimes a little confusing for the first-time purchaser.

We've gathered together our three top-selling players and put them side by side so you can compare features and decide which one best suits your lifestyle. Listen to the radio a lot? You'll probably want a player with a built-in FM tuner. Like a player you can trick out with accessories? You'll want one that has lots of add-ons available.

	Apple iPod® nano	8GB Apple iPod® touch	Sony NWZ-B135
Music Store Download System (learn more)	Closed	Closed	Open
Capacity	8GB	8GB	2GB
Music storage (@256kbps)	66 hours	66 hours	16 hours
Music formats supported	AAC, AIFF, MP3,WAV Audible 2, 3, and 4	AAC, AIFF, MP3,WAV Audible 2, 3, and 4	WMA, MP3
Video storage	8 hours	10 hours	N/A
Video formats supported	MPEG-4, MOV	MPEG-4, MOV	N/A
Image formats supported	JPEG, BMP, GIF, TIFF, PNG	JPEG, BMP, GIF, TIFF, PNG	N/A
Built-in FM tuner	No	No	Yes
Built-in microphone	No	No	Yes
Built-in Wi-Fi®	No	Yes	No
Built-in Bluetooth®	No	No	No
External memory	N/A	N/A	N/A
Accessories included	Earbud headphones	Earbud headphones	Earbud headphones
Third party accessories available	Many	Many	Some
Navigation	Click wheel with center button	Touch screen	Button controls
Dimensions	1-9/16"W x 3-5/8"H x 1/4"D	2-7/16"W x 4-3/8"H x 3/8"D	3-9/16"W x 15/16"H x 5/8"D
Weight	1.3 oz.	4.05 oz.	1.02 oz.
Price	$149.99	$229.99	$59.99

Open and closed systems

The primary difference between players is whether they're part of a closed download music store system, or an open one. Closed systems have all the elements — online music store, PC music software, portable player — fully integrated so they work together seamlessly. Apple is an example of a closed system company. They operate the iTunes® Store, provide the iTunes software for your PC, and make the iPod® portable players. Store, software and player use Apple's proprietary AAC music file format — a format that's not compatible with any other download store or brand of portable player.

Open systems offer a selection of music stores and portable players from various companies. Because they all share the same music file format, you can mix and match players and services. Microsoft's Windows Media® Audio (WMA) format is at the heart of the largest such open system. Online music stores such as Napster and Rhapsody use WMA files encoded with a form of digital rights managment (DRM) copy-protection for their downloadable music. Microsoft provides the Windows Media program for PCs that reads and manages these WMA files, and diverse companies such as Creative Labs and Toshiba manufacture portable players that operate in Windows Media and use WMA files.

It's important to remember that the terms "closed system" and "open system" only describe the online music store-to-software-to-portable player relationship, and the copy-protection their respective formats use.

In both kinds of systems you can download and play MP3 files from legal download sites such as eMusic.com and Amazon.com, as well as other sources such as band websites and podcasters. Both systems also let you import music from your personal CDs to your computer, and transfer the songs to your portable player as either MP3s or the preferred format of the system you're using (that is, AAC or WMA files).