My computer EXPLODED... or so it seemed...

[GibsonSGKing]

I heard that switching to the UK 230 setting while in the US just doesn't allow the computer to boot but if you are in the UK and switch it to US setting will fry components since the psu will be set to receive 110v and receive 230v and break the psu

Pretty much. You can obviously see that more voltage (More than double in this case) is certainly a much bigger problem that less voltage. Electricity is not something you want to mess with, especially not in Europe. It kills, plain and simple.