My PC has died

Hey & ty for taking the time to read this post.
I was watching a movie last night when suddenly the pc seemed to turn itself off. This hadnt quite happened, the fans went off, screen blank but the power light was still on.
I turned the pc off and tried to reboot but am greeted by blank screen(my monitor seems to get no input)and even thought the power light & fans start to run the keyboard lights dont respond or the mouse and hard drive activity seems to be zero. Please can u guys try to help?
Many thanks Gary