My Computer Shuts Down Automatcially?

The computer im useing right now is my sisters' Dell labtop.I Have a Dell labtop to but the keyboard had water spilt on it and the keyboard dont work.Im 11 SO i play the sims 3 on THAT computer.And also the charger if you move the charger outta the eletric thingy on the wall,or you pull out the charger from the computer it turns off.And while i play the sims 3 sometimes when im done building my people and house it shuts off completey down.What is it doing please help?