On a system that's starting its teenage years, it could be anything from worn-out components on the mainboard (voltage regulators being the prime suspect) to a faulty CPU (these are similarly aged and unless you know its history, it could be the equivalent of a replacement engine with 300,000 miles on it). If two CPUs haven't worked, chances are you have a marginal system board. 
Hi All, Well I am finally installing all my new upgraded parts (still searching for a 5000m graphics card & heatsink), however after installing the i7-940XM CPU it will not start. This is the second CPU I have tried with the same result. Has anyone had similar problems when installing this CPU? Some insight or suggestions on solving this problem would be appreciated. TIA Mark
Precision M6500 will not start after installing i7-940XM CPU