Bricked Onda v919 64gb (without 3g)
It sounds like you have corrupted your partitions. To fix this you either need to rebuild your partitions (which requires a knowledge of the device and MBR or GPT, and will need know how the factory ROM is imaged).

Or you can repartition your tablet by flashing it with a factory ROM. This will revert the tablet back to its original state. Thus erasing all of your data.