When I turn my phone on all I get is a white screen?

I was trying to check my memory status on my Sony Ericsson W300i and all of a sudden my screen went white. I tried turning it on and off, taking the battery out, taking the sim out but whenevr I try to turn it on nothing happens apart from me getting a white screen. Once I turn it on I cant turn it back off either. Please help me if you can!!
xx