Answer to: Why is my pc's screen black when I turn it on?It could be an overheating problem. Something similar happened to mee with my HP Touchsmart 300-1000. Opened followinf this instructions (http://h30434.www3.hp.com/t5/Desktop-Video-Display-and-Touch/HP-TouchSmart-300-1120-not-booting-up-and-with-noisy-fan/td-p/4522598) and then replaced the thermal paste. The problem might show up again later on, so keep in mind to repeat the steps if you don't want to spend on a new system. Good luck!