Hi there, and welcome to PC Pals.
I'm no techie myself, but it does sound pretty terminal, doesn't it? I would assume your PC (although switched off) was still connected to the mains when the surge occured? Sometimes a surge protector can help, but apparently they are only effective for one 'strike', then they should be replaced.
As I said, I'm no techie, so keep checking back here, and hopefully someone else will be along later with some suggestions.