You will need to reflash the firmware to format the player, see the answer I've just posted to question 'Matsui 120MR 2GB mp3 problem?' for details of where to get the firmware.
If player doesn't turn on to enable reflashing unplug the player then hold play button while connecting until PC asks for a driver - the recovery driver should be included with the firmware.
If there is anything important on the player then once reflashing tool has detected the player the PC should give it a drive letter to allow files to be copied off before reflashing (which may wipe all data off the player)
Nigel
June 2007