If I leave my pc in standby mode and return to it later on it appears to be ok, 'pc' showing on tower display and monitor light at amber. if i press a key on the keyboard, monitor light goes green but then back to amber and nothing comes onto the screen. What I must do then, is to turn the pc off and turn off the mains supply and leave it for several hours, after which the pc will turn, boot up and operate normally....any ideas please