Seagate external hard drive failure

bring it to a local computer store and request data backup
if its clicking its close to failing
you have bad sectors they are created when the hard drive head scratches against the platters if you wait the bad sectors will just spread

There's a Hungarian company called "Kürt". They're the kind that opens up the hard drive in a laboratory and take out the platters so that no further scratching/damage from bad mechanics occur. Unfortunately they are pretty expensive (a 400-1100 GBP for a hard disk drive, converted from HUF (Hungarian Forint): http://www.kurt-datarecovery.com/en/prices ), but I guess that's what it means to be professional.

I'm not sure how/if they provide services internationally. But if you have the money, and your data is irreplaceable, you surely want to chose a company like this caliber, not your neighbour's little son.