I have an inspirion 9400. When I plug in the power supply to the laptop (it blinks green, usually it just stays green if the battery is charging) then turn on the laptop it powers down within a few seconds (when laptop is on the battery icon turns orange like there is no power and as if it is not plugged into the wall). I have tested the power supply at a local comp store and they say it is alright. However when I take out the battery and try to turn it on still nothing.

I waited a day and tried to start the computer this morning and it did boot up into windows for like 3 minutes and then shut off. Now when I press the on button, it turns off within seconds again.

What do you guys think the problem is?

This might be just coincidental but before this happened the screen started flashing all different colors, so I restarted and then this problem occured.