Hi mary
Has you got no power to your pc first check the plug ( no lose wires and that the fuse is ok ) if they are ok then it might be the power supply unit
( this is inside your pc) if you have a spare one change them over
or get it checked from your local repair shop.
i know you said you checked the power supply but i not sure if you have checked the one inside your pc.
hope this is of some use if not post back
dave

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