HP DV8000 failure to boot

Hello All,
Desperate for some help. I have a DV8263 ea HP Pavillion laptop that isnt booting up. As soon as i press the power button the left blue light at the front comes on and the computer sounds like it is kicking in and then the fan stops but the lights remain on the HP Quickplay bits and the powerlight at the front is on but not the HD access light. The screen does nothing. I have tried to plug in an external monitor in case the screen isnt working but that doesnt nothing. Any idea what it could be?
 
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