hello i'm new here, i have a dell dimension 3000 here, it belongs 2 my aunt, during a bad lightning storm, she turned her pc off by the power button, the next morn, she tried 2 power it up, but no power.. The light on the board is lit but that's it...I have tried different power supplies and memory, but no luck...I tried disconnecting the cables also and just use the power supply cables, still no power, can someone tell me what else to do....

I think she may have forgotten to disconnect the net cable... and the mb got a jolt from that? May mean a new mb; ram, cards and cpu may have survived, may not have. Get it checked at a dealer's who has a tech on hand.
The sys will run POST and other checks with only one stick of RAM installed, so you can try with no drives hooked up, remove extraneous cards also.

thanks gerbil, she was struck by the lightning, well 1 out 5 tvs were hit...

FIVE tvs!!? It was doing her a favour...