Sony Vaio notebook

I have a vaio notebook and it is old and running slow. We have purchased a new notebook and I decided to clean out the vaio to try to get it to run faster. I pulled apart the body of the computer to blow out the dirt and dust. after reassembling it the computer powers up and apears to be working but the monitor will not do anyting. is there a way to test the screen on the notebook and if so were am i looking. this computer is old and not worth much to me. I am wondering if I should just scrap it and not spend any more time on it. Thank you.