Computer shutting down repeatedly

[toshibauser]

Hello,Hello,
I have a Toshiba L305 Satellite laptop.It had windows vista OS. I tried to upgrade it to windows 7 but the upgrade was unsuccessful and a message was displayed on a windows 7 background that it would revert back to the older OS. It kept rebooting every time and shutting down with display of this message. Since the computer was not working anyways I took this as an opportunity to disassemble the system and clean it inside out as I had'nt cleaned it since I bought the system. After assembling back the system,, when I boot the system the computer after the POST displays the same message and shuts down but the difference this time being it does'nt reboot back on its own.When I start the system the second time it shuts down much quicker many seconds even before the message display.The same keeps repeating everytime. Booting for a a minute or two the forst time followed by a shutdown and then after rebooting shutting down much quicker time. What could be the problem PSU or excess heat at the CPU.

 

[hang-the-9]

Could be either, how far did you take it apart?