When I was looking for a MP3 player, I wanted one that did not require it's own program to convert and upload to the player. I wanted one where all I had to do was plug in my player and it will show up as a removable drive in Windows Explorer. Then drag and drop any MP3 file over with or without folders. The Sandisk Sansa supports exactly what I wanted. Not only that, it also has support for Windows Play for Sure that's included with Windows Media Player 10. This lets you easily send music files to Sansa from numerous online music sites that support Play for Sure.
I loaded a few songs I had on my rig to run some initial tests. I did a few at set bitrates and a few at variable. All MP3 files were stored in it's own directory ordered by the album they belong to.
Once you press and hold down the menu button, the unit will turn on showing a few welcome screens. Press down on the menu button again and choose Play Music.

You will be presented with the option to Play All music files or choose from Artist, Album, Songs, Favorites, Genre, Year or a playlist. Most of the information is retrieved from the ID3 tags from your MP3 file.

Once you start playing a file the artist's or band's name and track title scrolls across the screen. On the bottom you will find the battery meter, bitrate and the repeat/random icons.

When your song is playing, press and hold the middle round select button to add the song to your favorites playlist.

If you press the Menu button and then choose Settings, you can access the equalizer. Depending on your music, you can choose from presets like Rock and Jazz or play around with your own custom settings.
