My hp laptop won't turn on!!

Hello,

I use HP dv4-1240TX.. the other day, i was using my laptop and it got overheated so it went into hibernation. I waited and turned it on again coz i was working on something really important. Then it happened again. I turned it on again when suddenly, the laptop's lights started dimming and it got turned off. Ever since, it wouldn't turn on. I tried hard restting it, but it didnt help. With the battery it just wouldnt turn on at all, but when i plug in the AC and switch it on, the power comes on just for a second and gets turned off. and the AC supply gets disconnected. And nothing else happens. It did got switched on once, but that was only for a minute and then it got turned off again. Please help! I still need to work on my important project!!