Is it a computer box problem and what is the solution?

Your logic is all messed up. Nothing works, so you ruled out the battery? The battery and cable connections would be the first thing to suspect. I'm not sure how you figure the Engine Computer would cause the power locks and windows to not work. That computer is not a suspect for those systems.

Did you "wash the car" or wash the engine? If you washed the engine, you may have disturbed an electrical connection that was about to cause trouble on its own. Clean and tighten the battery cables. Also, follow the smaller positive battery cable to where it connects to the under-hood fuse box. Shine up that terminal with sandpaper and be sure it's tight. Follow the smaller negative cable to where it bolts to the body and be sure it's tight.