Previously i had windows 8 installed and changed back to Ubuntu, i think Ive messed up the hdd drive (freecom 500gb)
To clarify, based on your additional comments:
If you converted your Ubuntu partion into an NTFS formatted drive, then yes, your Ubuntu installation will no longer work, regardless of whether it was on an external HDD or not.
It sounds like you're going to probably need to start over. Ubuntu would want (by default) an ext4 formatted drive.