how can i fix my sony ericsson w810i?

i dropped my phone and it turned off, i turned it back on and it said in active sim so i re put the sim in and that didnt work, where it should come up start up phone or use music it coming up select and info on a blank screen and wont let me access into my phone. after a short while it comes up with still a blank screen but a key is on the left hand side?