i have been using w10 happily for the last week with no problems. now in the last 24hrs i cannot turn my pc off if i choose shutdown in the power option in start menu. if shutdown is chosen i am told shutdown is taking place....little circle spins and screen goes black. then a few seconds later the login to w10 screen appears!. during this the pc in now way powers down.... my tower stays on and all fans etc do not power down. i have changed nothing myself.