My camera wont turn on

okay i got this camera and i used it for 2 days 4 the big feild trip and i go to upload all of the pics and when i press on button it doesnt even turn on
Camera won't turn on after it went off during loading pictures to the computer. I have tried fresh batters, connection to USB AC adapter. Still no power shows on the camera (green light won't turn on).
Help !!!! my digital camera won't swich on. The battery is fully charged but i can't switch it on. Why?