Windows wont start.

Hello,
My acer laptop wont start windows. It wont even get to the log in screen. When i turn it on it gets to a screen that says run on repair(recommended), or normal. when i start it on the repair, it will just load for as long as it has power. and when i choose normal, it will load and go back to the original screen.I'm kind of desperate as there is vital things needed on my computer. any help or advice at all will be greatly appreciated. Thank you for your time.