Hello, I was trying to reformat an external USB hard drive that had always worked fine (it was completely readable/writable). When I first tried to format it using Disk Utility it stopped mid-way through the process, telling me that an application was using the disk. I restarted the computer and tried again--same message. I'm pretty sure it was referring to Spotlight's indexing of the drive. I restarted again and tried to format the disk when Disk Utility froze. After trying to unmount the disk and failing to get Disk Utility unfrozen after a few minutes, I pulled the USB cable out. Since then, the disk has been clicking and clicking and clicking--won't mount, won't do anything. The drive in question is a Serial ATA Seagate Momentus 5400 that was originally the internal hard drive of a year-old MacBook connected via an enclosure. Any advice to bring this disk back from the dead? What went wrong?