Computer failure for unknown reasons

[evt]

Me and my brother have built a PC for a friend of ours. 2 weeks ago, the PC just dies out of no where, no POST or beeping. Removed every component except for the bare essentials. Long diagonistic story short, its 90% chance that the motherboard is shot with no visible damage/smell (budget Biostar board), so we bought an exact motherboard replacement and the computer is happy.

Until a few days later, it exhibits the exact same symptoms. Not wanting to reinstall windows, we have decided to get a different manufacturer branded motherboard but with the same NB/SB chips, as well as a new PSU to rule out that failure. All is well...

Yet another few days later, the PC is broken yet again, and I am completely stumped as to why this is happening, since I can only think of very far-fetched reasons:

Bad electrical outlet (highly doubtful since everything else that is plugged in works fine)

Heat (I would assume the damn thing would shut off automatically before it would reach damaging levels or BSODs)

GPU / RAM / Hard drive killing the motherboard

Extreme bad luck


Anyone have any possible reasons?

 

[Dangman]

Electrical issues might explain the hardware deaths and instability actually.

With that said, replace the RAM as that's the only part out of the three you listed as possible causes that would have the potential to cause system instability.

Also, try another CPU in that system. Maybe the CPU might be defective.