While Xell can read the HDD, you will need to format it with linux(ext2/3/4, swap), or fat32 partition, and then put the kernel elf at the root of the drive, if I remember correctly. this will make the hdd null and void for regular xbox 360 use, as that uses fatx partitions. I dont know why Xell, and LibXenon dont read fatx partitions, as I know there is native linux support for this, or at least for the original xbox.