Replaced mother board and hard drive now the inspiron wont stay on

ispiron 8600, had a 9 light blinking issue, decoded it, replaced mother board. while i was there replace hard drive. put it all togeather. now have other issues. plug in battery. battery indicator lights up(good). depress start button, the three led lights green for about 5 sec`s then lights out. doesnt start or stay on. also i can hit f12 while green lights are on the battery light goes to yellow, fan turns on and then i cant turn computer off with button. did i get a bad Mother board????