I can't switch on my MP4 2.8 TFT Touch Screen 8 GB
 

For a half year, everything was ok, but now the player doesn't start. If I connect the player per USB with my notebook, I can open the player and all folders are there. So the player can't be dead at all. When I connect the player with the aku cable, I can get to the main menu and can do everything but when I take it off, nothings works. The player is off and can't switch on. I already formate it, but it doesn't helps. Has anybody a idea?

Possible battery problem!
Might need to open the back cover and test the battery.

Have you tried charging it through both the USB into your computer as well as the wall charger? If you've tried both then the two possible reasons is:

1. Your battery is dead so it can't hold the charge anymore

2. The charging ports on your player is faulty and so not passing the charge to your player's battery

If your player works fine when plugged in then it seems most likely it's a faulty battery than anything else.

I don't know what your player is and what the inside is but if you can try a replacement battery that might work. It really depends once you've opened up your player.....