I'd love a HD Tune Pro 5.70 Portable!
Version 2.55 appears to be available portable, but that doesn't support hard drives > 2 TB.
I googled a few elsewhere; some sites looked particularly dangerous; I tried to download one from [link to illegal software site removed by mod JTH] and Chrome said it was virus-infected.
I own the program so I asked http://hdtune.com/ for a portable version but no success.
It's the very best hard drive diagnostic utility I know of; whereas the drive manufacturer's versions report only errors greater than a certain threshold, HD Tune reports ALL error.