I had some hard drives that were working fine at the time that I sold them. The individual I sold them to had a 2.5" USB 2.0 Aluminum Serial ATA (SATA) Hard Drive Enclosure which he used to test the hard drives. He came back stating that one of the drives was not functioning correctly. I thought it odd, but I took his word for it and allowed him to test a few more drives before he left and he took 2 more that he was pleased with. Now he's contact me stating that the total of 3 drives he took failed a drive test. So I am probably going to refund him his money. However, I got to thinking that he was using the USB enclosure and just pulling the hard drives out and popping them in while the computer was on. Is it possible that doing this could have damaged the drives? Not once did I see him selecting "safely remove this hardware" so I'm suspicous as to why these drives would fail a test. Thank you for your responses.