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Lower down the board, below the graphics card whose fan and heatsink assemble occupy the top half of this image, are seven green LEDs mounted directly on the board. As you can see from the logos, they provide POST diagnostics (from right to left): CPU, memory, video, optional ROM, USB, hard disk and OS start. If any of these devices fails, the LED glows red and a beep sequence lets you know what the problem is. Also in this shot are, on the right, the front panel indicator headers (as fiddly as they always are) and on the left, unused auxiliary fan and S/PDIF headers.