Sounds like you killed the battery.
I have a mini generic MP3 player that does not work by itself as it used to. I can charge it to the PC and it turns on and I can download and upload music files fine. I can use the PC Media player and it plays all of the music within the mini mp3 player fine.
Problem is that once disconnected it will not stay on or work by itself. How did this happen?
Before I would plug into the computer and it would charge itself up then I could unplug and listen to it with its own power. Natuarlly, I plug in some headphones. Thanks to my great wisdom I noticed that it had the same connection as my cell phone charger. You guessed it. I plug the cell phone charger and everything look ok. It lit up and looked like it was charging. From that day forward it has stopped working on its own power. I think maybe I fried it (you think?)? Or maybe the drivers in the MP3 were erased.
Does anybody have any idea how to load the drivers back into it and see if it does work? It is just a generic brand. Mini, has a small window, Has a master button with M on top and VOL at bottom. The left and right side are for increase/decrease of volume or change to next selection. The middle is for play/pause.
Good luck with this one....

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