Recently I have build my parents a office pc and I decided to use their old hard drive on it to save money so I reinstalled windows 7 on the hard drive, it was going well until it said that it'll need to restart the computer to continue installation. However once I click ok, the screen goes black but the power is still on... The fans are spinning and everything, it stays like that forever, I left it on over night just incase but no sign. I realised that the computer will always do that when told to restart. Please help, anything will be grateful, thanks!