It turns on, but the screen is blank

Hello, I need an answer to a problem, my grandmother's computer hasn't been working for the past 2 or 3 days, she tried to get on it yesterday, it would turn on, but the screen was blank, nothing..... (yes I still have a grandmother)
Nothing here realy helps cause it requires a battery, she dosent have a battery in her computer. I would REALY like some help please