Try plugging it into a computer with a different operating system. Do all of these computers have the same operating system?
I had borrowed a 120 GB Fujitsu external hard drive from a friend. I plugged it to my old laptop on which I had run a virus scan and cleaned off all the viruses. The hard disk got recognized this time. Then once I unplugged this and plugged back later onto the same laptop, it wasnt recognized. I then connected it to a brand new laptop and it still wasnt recognized. I tried connecting it to few other laptops and it still wasnt recognized. That makes me believe that the hard disk is infected. Can anyone please help me with this issue.