|It might just be bad.|
Was it previously recognized on that computer? Is it seen on other computers? Does it work OK when you use it to play mp3s or are you having problems with it separate from it not being seen by your laptop?
The requirements for it say it needs WMP 10 and a USB 2.0 port.
The support page shows a 'sansa firmware updater for PC users':
You might want to give that a try.