hi, my cousins pc stop displaying an output signal to the monitor today and he's not sure what to do about it. its has built in graphics with both dvi and vga output. currently using the vga output, i suggested he try the dvi (which he hasn't tried yet). when it boots up he said all the fans and hdd are working but no output on the monitor. tried another monitor same result. any suggestions? pc is a core i3 with the basics, purchased from pc world.