Please help my laptop

One day I turned on my laptop and I typed my password and the laptop says "we don't have enough source please type your first password." But I don't even have second password what I typed was first password. Than soon black out I can only see mouse sign.(the sharp thing that we use to click) my lap top is Acer and can not remove battery by my self and I want to fix by my self and my parents must don't know about it. So please tell me what should I need to do for fix my laptop cheap, quietly and fast.