j'ai trouve ca sur un forum anglais; tu peux toujours essayer
Here is a detailed explanation of what worked for me, I had the same problem you did.
1. Assume ALL FILES ARE LOST on the drive. You're SOL on these files (you may be able to recover the contents of many of them after the procedure, but don't get your hopes up)
2. Download the free Active Kill Disk from http://www.killdisk.com/
3. Unzip and run Active Kill Disk. It will display the message that it supports "[ONE PASS ZEROES]" method only. Remember this.
4. Press enter to bypass the startup screen.
5. Scroll down the list to view your drives. Also, open up My Computer so that you know which drive letter your USB Key ISN'T. You will probably find a message of a drive not being ready, if you find this message, highlight that drive, otherwise highlight the drive that does not have the drive letters of the workable drives of your computer.
For example, in addition to my main hard drive C: I also have a big hard drive E:. These show up as fine since it was my USB key (which is on F:, but that doesn't matter now) that was damaged.
6. Press F10 and press enter to erase the disk (using that [One Pass Zeroes] method mentioned earlier
7. Go into the Administrative Tools (this guide is assuming Windows XP) and select Computer Management. Double-click on Disk Management.
8. Go down the list of disks until you find the new healthy partition of the USB drive. Right click it and say format. Format it whatever you want. If after the attempted format it says something like "I can't do this because the partition is write-protected," ignore this message.
9. Go down to a green icon on the taskbar with an arrow on it, click it and say to remove your usb drive. After it says you can remove it, do so.
10. Insert your USB drive again. Even though disk management said you couldn't format it, it did most of the reformatting and you will be able to recover any undamaged files from the combination of reformatting/erasing.
11. Once you save any files that you can, reformat the USB drive (you won't have any errors this time) from My Computer. Remember that the reformatting will erase all the files on the drive. Once this reformat is complete you'll have your USB drive working again!
