I was copying data from PC to my Lacie external 500 GB HDD. And Simultaneously I was accessing files on my PC and on that external HDD. but after some time File System stopped responding and showed the error saying Videos folder is not responding and gave two options as Force Quit or wait....I chose Wait option but it didn't work and showed the error again. So I clicked on force close and System stopped copying the data. Now the system detects the external HDD but I'm not able to mount it. System shows the error message saying input/output error. So How can I solve this problem without Formatting my external HDD ? Refer Following Link for screenshot https://docs.google.com/file/d/0B4rWcneEmcfTSWRFSS1QX0F6bHM/edit?usp=sharing. After that I even tried to live boot the elementary OS Luna from USB thinking that my external HDD might get mounted but it didn't work.