Dzul SK :
So basically my computer got struck by lightning even i turned it off.
If the cables were through the plug, even if the switch was closed it would destroy your PC due to overvoltage and overcurrent. Overvoltage will allow some equipments to turn on and overcurrent will cause fuses to blow. Power supplies are not designed to allow a fuse to blow. You need an electrician to check the wirings in your house to replace your wirings that have been affected by the lightning and make sure he replaces your breakers.
Some third parties sell surge supresser that sites in your meter socket. If this is a somewhat common occurrence in your area, it would be a wise investment even if it doesn't completely prevent damage, it most likely would have reduced the scope.
Remember next time to remove the cables connected to the PC as it will fry your equipment. If you have a warranty then get a replacement for your damages.
Hope this helps.