I have a 4 gb Sansa Fuze that was working perfectly up until today. Over the past two days I was using my dad’s laptop to charge, something that I had done before, and tonight when I tried to plug it into my own computer I’m now getting an error message saying that the driver isn’t recognized. I’ve tried changing the USB format, holding it off for 10-20 seconds, and nothing it making it recognizable.
Possibly insufficient power. Try using the USB port on the back if your are using a desktop. BTW, what type of operating system are you running? If your Sansa still powers on, try switching to a different USB mode under Settings.
Try the steps found here as well: Sansa player not recognized by the computer