take out the battery, connect the ac power adapter, turn on the notebook , move the power cable near the notebook connector to check the connector in the notebook is losing or not. ( or even with the battery in, because the notebobk should have the light or in xp should have a icon on the right hand side button coner to show is using battery or ac power ).
if is over heating problem, normally, u can't turn it on again directly, have to wait a while