sony hd3 mp3 player

I was bought one of the hd3 players. At present all was going well. At the moment however I my pc won't recognise my device. The player powers up and displays the walkman logo and then turns off after a few seconds. The "pc connect" does not appear on the player screen and the option to transfer music to the player is not available. I have tried installing the software from disc again but with no success. Any help/advice would be greatly apppreciated. Thanks