How to solve booting problem on Lenovo G570 laptop?

My Lenovo G570 laptop is failing to boot up. The Windows start up is running well but the machine is failing to display users. It keeps trying to display users, loading and failing and starting all over. I'm virtually locked out of my machine. Is there any other way of booting up

This is generally missing system files, in order to save time, you can try to reinstall the system! Note that the C disk backup important files! If you can't find someone to solve.