Computer totally dead although led is on

Hi when I connect the computer to the supply led lights on but it's totally dead. Is there a step by step to see from where the fault is?

Thanks

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crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0