My laptop doesn't turn on anymore

Hello,

I need a help! please help me regarding my laptop, i cant use it anymore because it wont boot up.I just insert an external memory in my laptop just to save some of files in there, after that i off it and when i try to turn on again i wont boot up anymore.I remove the external memory but nothing happens.the first time i open the laptop after inserting the external memory a message appear critical batty low! something like that.Then everything black nothing appears.What should i do in order to fix my acer laptop. Thanks