Why the computer is on but the screen is completely black
crwdns2934249:0crwdne2934249:0:
I upgrade my Windows Vista to Windows 7 Home Premium, before that, I run Windows 7 Upgrade Adviser, it said I can run Windows 7 Home Premium and Windows 7 Ultimate. After upgrading, the computer work fine, I made a system restore just in case. After turning off the computer, next day I turned it on and the screen is completely off, the fan is on, the computer is on but the screen is blank, everything is plugged in but, pls help me