Try re-formatting your thomson player using the firmware update program provided by thomson here:
http://209.85.135.104/...
be sure to enable the checkbox "format data...". this will re-setup the data sector of your player. note though, that all data currently on the player will be lost. when you hit start, the program will first attempt to install a new driver called "thomson recovery device" or similar. you might have to press a button to continue the driver installation. after installing the driver, the updater will try to find your thomson device. for some reason though, it will complain after a while that no player is connected to USB. if that happens, just exit the update program and start it again. when it comes up again it should now find your player and show status "ready". now enable the checkbox once more and click start. the update program will now re-format your players data section. wait until it is finished. after that you should have your thomson player back the way it was when you purchased it.
note: when going through this procedure i noticed that for as long as my player was in "recovery device mode" it would not work, meaning that i could not switch it on, neither would the drive show up when connected to my pc. however, the update program would still recognize the player when attached. once i successfully re-formatted the players data section, it was back in "normal operation mode", working fine again.
hope that helps!