do NOT unplug your xbox untill it is fixed......
try reformating C:
Format partitions by sending 2 raw FTP commands to the xbox for each partition to format. The commands are as follows:
a. Formatpath \Device\Harddisk0\PartitionX
Where PartitionX is either 1(E), 2©, 3(X), 4(Y), 5(Z), 6(F), 7(G)
This will give you a key, something like:
200 FormatKey key for '\Device\Harddisk0\PartitionX'. Where key will be a 4 byte value in hex (8 characters)
b. FormatDrive key
Where key is the key returned from command a.