I could listen to some songs

Make sure the files are all compatible with the device (probably Mp3 in this case). Check your instruction manual to find out which files will work on the device. Also, try testing the songs on Windows Media Player. If an error message comes up, the mp3 might be corrupt or has an attachment that makes it not able to play.

well, first format the sansa player on ur computer, then reaply ur music and find a better quality song like that 1 to put on it, i recomend buying it off itunes or something like that, because it could have a virus in the song or it cannot be played on the player, (via: it is not the right format to be played on it, like mp3 or wma files.)

My dad tould me to use Windows Explorer instead of Windows Media Player to delete the files.
WOOT

You have songs that may be protected or the wrong format for your device.
delete the bad song and download another copy from a different source and try it.
This is not to uncommon due to different file formats and protection in the song files
When you rip songs from another device often some won't load or play in another device
especially if they are paid for songs.

try re-adding all audio cd songs in to you WMP11. Instead of playing what already in there.

Go to now playing and try adding all tracks into it.

Download the latest firmware upgrade for the device at www.usasupport.philips.com
The firmware upgrade will delete all songs off the device
Re-add the songs you would like
It should work better the second time around

same thing happened to me it still doesn't work and mine is supposed to hold 500 it only holds 150

Yeah, I have that "Bad Track" problem for some my tracks or even for entire albums. The only thing I can think of that would cause that is if you skip over the track consistantly. Anyway, the best solution I've found for that is to go to Windows Media Player, delete the track, and then put it back on if you have it backed up on your computer. P.S.: MAKE SURE YOU HAVE THE SONG BACKED UP ON YOUR COMPUTER BEFORE YOU ATTEMPT THIS. If that doesn't work, you should find another way to get the song. Unfortunately, I can't help you with the "No Files" problem since I haven't experienced that.

I think you need to format your player. Open up my computer, right click the player and click "format"

Have you tried updating the firmware. Even if it is the lastest edition, download the firmware manually and run the software. Then format in Windows Media player. Best Regards Keith