Computer has been going black

Hi,

My computer had been going black whenever I've tried to turn it on since about an hour and a half ago. It came up saying 'start windows normally?' And 'Reset to figure out problem'. I accidentally clicked on the first one, and now it is stuck on 'Starting Windows' with nothing else on the screen...please help!! (I'm only in year 8, so please try to word responses easily to understand)