Compaq laptop screen wont turn on

Hello,

The power light comes on and it makes noises like it's turning on and working but the screen never turns on. I tried just pushing random buttons. I.e. the monitor function some key that says 'sys rq', ctrl alt delete the windows key, etc. I don't know what I typed and in what order or how long I waited but it worked! My laptop worked fine all day after that. The normal Windows start up came up, but when I shut it down it runt start again. How do I fix this?

Regards