Saxat från ett annat forum:
Turn on the phone without Simcard.
Then go to hidden menu (turn jog dial up * jog dial down jog dial down * jog dial down *).The menu will pop-up.Go to Service Function.You will be asked wheather to format the disk or not.Format the the Internal (C: Disk You will loose all data ).
If you are not able to go to Hidden Menu Then take your phone to SE Service Center.