I really wont know what to delete if i rejailbreak it and then use iphone explorer.
There is a method where
''involves restoring the phone as a new phone, then jailbreaking it. Once the user has shell access, umount is used to force the two mount points into read-only mode. Now the partitions can be overwritten with /dev/zero, which should wipe them clean. The phone should then be forced into recovery mode to perform another full system restore, and the process is complete. Several iterations of the process with /dev/random should prevent even NAND recovery''
i think somehow cydia has created a small patition on the phones hd which was wiped but the parition is left as other, but thats just my taking on it