Typical situation in trouble shooting a computer - any little mistake will cause you chasing around, looking up and down, and still scratching your head.
I sent the processor the computer shop yesterday for testing and to my surprise, the processor was alive and kicking. In light of that, everything point back to the motherboard again, either the new one also faulty or i didn't install properly even though i am already careful. And yup, it turned up it's the later. I'm not aware what i missed during installation but i'm happy the whole thing finally end.
Unfortunately with new m/b, my Vista unable to re-detect the new hardware and thus failed to log into Windows. Using Vista CD to repair the OS also failed and i end up reinstall the Windows. At least my old files (including DAO and ME2 saves) were saved into "Windows. old" directory.