MY SONY WALKMAN CANNOT BE OPENED, IT LIGHTS UP THEN TURNS OFF IMMEDIATELY
What do you mean "MY SONY WALKMAN CANNOT BE OPENED"? If you mean that you can't get to the battery, then you should look at the charging piece in the MP3. If it wiggles or moves in any way, then there is no way to fix it. I myself had that problem once, and it needs charged, but won't take a charge for some reason. I glued the piece in place with super glue which didn't help, and even put a drop of water on it to see if the electricity needed a material to carry it. That didn't work either. I gave up, as there are no screws, so you can't put it back together. I would suggest getting a new one, getting a new charger, or taking it to the store you bought it at. If that doesn't work, then bring it to RadioShack and ask for help. It's worth a try. Or, as I always add at the end, continue looking on the computer.