My situation is exactly the same that the person asked with the heading: My computer turns on for 3 seconds, then shuts off. There is no beeps saw posted that you can trouble shoot that way. It all started because I decided to look into moving to windows 7 after being on the microsoft website I downloaded the fix me tool and it was titled performace issue fixer. It said it needed to be restarted and I did that. Went out for a couple hours and came home to it turning on for 3 seconds then shuting down. I cleaned it checked with a new power cable and still the same issue. My problem is I'm not understanding what everyone was talking about with username: bicho83, well at least what was suggested for him to try. I'm great at understanding computers but when it comes to taking them apart can follow instructions but need specific details. Anyone that can help with in anyway would be greatly appreciated.