Right, to give the whole story from the start; I bought a new battery from eBay, opened up the back and fitted it. All quite simple. The next day, I turned on the unit and found that there was something up with the sound through headphones. I opened up the unit again and tried to fix the problem. After virtually taking the entire thing apart, I found that it was a loose connection (one of those flat copper things that has about 15 individual connectors in it), so pushed it back in completely, and closed up the unit again. All was well until I hooked it up to the USB port to try to transfer some new tracks. It will still charge, but the computer isn't 'seeing' it when it's connected to the USB port, and the screen has stopped working all together. I've tried everything I can think of, save for going to the Sony service centre (as I'm too poor right now) Does anyone have any useful input?