Error Code “O” in transferring files

Hello Everyone,
Can’t understand an error always occurs Code 0. Have 40 GB IDE external hard disk that has a fee space of 10 GB now because 30 GB are purely downloaded file.
Some files are moved to my PC with 500 GB SATA. Is there anyone encountered this error?
Please share!
Thanks in advance.

Error
Helper window (Code:0)
