.NCO File Extension
What is an NCO file?
Compressed backup file created by Nero BackItup (formerly Nero BackItUp & Burn); contains data to be backed up to a CD or DVD; compressed using standard ZIP compression; may also be protected with a password and encrypted using a 56-bit key.
NOTE: Since NCO files use .ZIP compression, non-encrypted BackItUp files can also be opened by file decompression programs such as WinZip or Stuffit Expander. Just rename the file extension from ".nco" to ".zip" and open the file.