I'd like to preface this post by saying that I am incredibly computer hardware illiterate.

The Hardware:
Seagate Barracuda 7200.10 500GB External HDD (ST3500630AS)
7 pin SATA
+5V 0.72 A
+12V 0.52 A

The Issue:
Some sort of read failure; when the drive is turned on, the disk spins up, but after about a second, instead of the normal read noise, it emits a series of five clicks, which then repeat at about an interval of 2 second. Most of the time, my computer detects the drive, but it won't let me access it (gives me a read error). Other times, the drive won't show up at all. In either case "SeaTools for Windows" app detects and recognizes the device, but it will only let me run the "Short Generic" test, which it strangely passes. As I mentioned, I am rather illiterate when it comes to hard drives, so all I've tried so far is reseating the cables, which predictably had no effect. Anyway, any ideas/suggestions would be greatly appreciated.

Oh, and the casing etc. is from a company called Moving Star--i don't know if that's important

Can be bad sector or Hw problem, should see it. If it is a head problem the drive needs servicing by a pro. If data inside not important, buy another one and forget it.