(redirected) my alienware r4 shutdown randomly

hi!....need help please.i don`t fire up my alienware r4( i7-3820,gtx560ti,2x2gb stock ram,875w psu) about 4-6 month.when im fire it up....it keep shutdown...even in bios.graphic seem ok to my eye on bios.try swap GPU and HDD to my other PC....seem running fine.so..im repaste the CPU....still have that problem.is that problem maybe cost by a CPU or Motherboard or PSU?the CPU have hole on it...is have problem is the termalpaste enter it?