I am running on Windows 7 64 Bit and a problem started 2 days ago. After few hours of using the computer, the screen randomly goes black. However my monitor indicates that it is turned on and I can change the Source to Freeview TV etc. My computer also has a blue light on which shows that it is turned on. However when the screen goes black, my music stops. Once this weird sound was produced in this process. I then have to unplug my computer to turn it off and when I turn it on again this problem repeats after few minutes.