I built my father a computer last year. Now it's not turning on. Well the power on the computer comes on, but there is nothing on the screen. Also the fan on the heatsink runs very slowly..all other fans run fine. He has a Biostar A880G+ mobo. Athlon II x2 processor. 450w PSU. I looked at it and everything is connected. He told me that he got a warning...something about the processor being 40 degree Celsius. Any advice would be appreciated. I don't think it's a PSU problem...mother board??