Np8690 shuts off when loading windows

Please help me I'm very very frustrated I I don't know what to do anymore. Basically I have a sager np8690 it has an ATI 5870 m and an i7 620 I thinkI cannot get it to load Windows phone nothing because every time I try to do it it shuts off I bought a new power supply for it I took it apart and put it back together I just don't know why it's not loading to Windows can somebody please help me figure out what I need to do to get it working again? What I can tell you that is if I put it into the BIOS setting section it will stay on for hours if I put it to the boot logo and press the pause button it will stay on for hours but once it starts to load WIndows that's when I shuts off as if it lost power

 

Does safe mode work?

 

Yes and no yesterday I have discovered that no matter which press why use I accidentally my screwdriver fell right on the CPU Port as the laptop became on and the darnest thing happened it booted right up. I had it upside down trying to test it , that doesn't mean that it wont shut down after a few seconds of being on, I think ram also maybe have a role in it as only a 2gb would boot to Windows and nether 8gb I got will get that far. After doing some tests if I tap the CPU heatsink and then press the power button it would boot normal but after restart it would go back to the problem, hope that gives you something to work on. And sorry for the bad English I used speech to text. I'll edit it when I get back

 

Could be a bad solder joint due to PCB flexing then. See if slightly loosening the heatsink helps.