I have a Sony Ericsson Z550i

I've had this phone for a while now, always worked fine, but this morning before school it wouldn't start, it showed a white screen then shut off again. I decided to leave it and try it again when I got back from school. It's still the same, white screen then nothing.
Warranty is over, someone got an idea what I can do?

I've had this phone for a while now, always worked fine, but this morning before school it wouldn't start, it showed a white screen then shut off again. I decided to leave it and try it again when I got back from school. It's still the same, white screen then nothing.
Warranty is over, someone got an idea what I can do?