Question: Are there any free tools available to perform hard drive diagnostic?
I have an old 3.5 IDE Samsung HDD which I use as an external drive through USB connection. I recently started to have problems with accessing some of the data.

Answer: 
Personnaly, I have used the following in the past:

* HD Tach from Simpli Software (<http://www.simplisoftware.com/Public/index.php?request=HdTach>)

or

* HD Tune from EFD Software (www.hdtune.com)

Cheers,

Thomas
You can grab Hiren's boot cd which contains some free tools for this purpose. [Website is here](http://www.hiren.info/pages/bootcd)

Maybe you'll have to attach your drive to the IDE bus for doing your maintenance work.