Toshiba Satellite laptop L40/L45 - itself going for shutdown

Hello,
I have a Toshiba Satellite L40/L45 Series laptop.
The problem is that it is turning off by itself after a few seconds of turning on.
It doesn't even get past the Windows loading screen and my OS is Windows Vista 32-bit. As I thought the problem occuring may be due to the battery I am using so, I tried to let it run just on direct power, but still there is same problem. The laptop is only 8-9 months old. So, if possible can anyone help me with this?