Re: Lightning Damage to PC
My first thought (hope!) was the PSU, but you already tried another with no luck. With all you did, it does sound like the motherboard is gone.
Surge and spike protectors are little more than fancy and expensive extension cords that do NOTHING for abnormal low voltage events, and merely chop off the tops (clamp) of the sinewaves for abnormal high voltage events - providing not-so-pretty (dirty) power for your PSU and motherboard regulator circuits to clean up. For these reasons, I recommend ALL computers be on a "good" UPS with AVR - automatic voltage regulation. I emphasize "good" UPS because like power supplies, there are cheap ones you should make every effort to avoid.
Note that power during a power outage is only the icing on the cake. It is the AVR of a "good" UPS that saves your hardware. I recommend all big screen TVs and home theater audio equipment be on a good UPS with AVR too. The downside is UPS batteries need to be replaced about every 3 years.
FTR, I have a 1500VA UPS with AVR that protects my fairly power hungry computer all my network gear (router, modem, switch) and two 22" widescreen LCD monitors. And it provides over 30 minutes of battery power in the event the grid goes down. If I shut down my computer and turn off my monitors, it will hold my network up (and all my IP assignments) for over 12 hours. Nice!
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Heat is the bane of all electronics!