I cleaned the Xbox 360 internal hard drive with the Linux "dd" command:
dd if=/dev/zero of=/dev/sdc
After this the drive is no longer recognised by the Xbox 360 (the drive doesn't show up in System->Storage Devices).
Is there anything I can do to make the drive usable with Xbox 360 again?
I have tried to create an exFAT partition on it but it did not help.