Ok, so this is long , please bear with me. I have had this problem for quite a long time . Often while starting up the computer , Monitor would display no signal detected and then it remains black . Often it crashes in the middle of something and then while starting it up the monitor displays the same message. The most ridiculous part is , it often solves when i keep the PC off for a day or two or a week. This happened a number of times. Then it completely refused to start again. Replaced my PSU and Mobo on the recommendation of the service guys and it was fine for a year and then again it has started. I cannot understand the problem. I can go and get a new Mobo/PSU again, but i feel its something else.