When I power on the PC all the thing is happening. CPU fan is running, Hard Disk is vibrating and CD writer is also responding but there is nothing on the the monitor. I reassembled many time the devices. I cleared the BOIS, RAM but nothing is happening. I see that problem not only in my PC usually this problem is happening in many PC but after some time when I reassemble, that PC start working but this time it is not working. So what could be the reason. Please suggest.