How do you fix sony Ericsson w550i white screen?

There could be two solutions to fix the problem.

1) You have to re-install software / software update your phone.
2) Its a cable (flexcable which is connecting screen to mainboard) inside the phone which is broken in some way, so you have to fix it yourself (don't do that) or go to the shop where its bought and get them to fix it through a repairshop!