Compaq Presario CQ40 Won't Turn On

On startup, you may see a blank screen. If the diagnostic utilities detect a specific problem with hardware components, the fan turns on, but the screen remains blank. To help identify the cause of the problem, various LED lights on the keyboard blink a series of codes.

The diagnostic utilities use the LEDs near the Num Lock or Caps Lock keys to blink a series of error codes. At the end of the series the blinking stops. The pattern of blinks will occur any time you attempt to start the computer until the error is resolved.

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