How to charge Sansa Fuze+ with Window 7 Home Premium HELLPPP!

Well I just got it yesterday , I didn’t even used it yet. I don’t  think if I hold down the power would resets the player since there is no battery. everytime I plug it in to my laptop the player it is connected  and on the right top corner the battery is full green but  I check the file of sansa fuze+ in my laptop ,it says: Critically low. Also if I unplug it , it would just die … Like there is no battery.