I can't believe you can't put 2 and 2 together
The thunder caused a power surge. The powers urge fried some components (exactly whatm I can't tell you) and now your XBOX is a very large paper weight. If it is still under warranty (standard is 90 days) then you're in luck, otherwise - sucks to be you, you're going to have to have to pay to get it fixed.
My guess: Your hard drive and/or mother board and/or processor are fried. Good luck