You may be missing the driver for the external hard drive. The easiest way for you to find the most recent driver is to search google for “[model name of HD] driver” and going on whatever result you get linking you to the company’s website. If you are using windows xp, you can click start, right click my computer, click manage. On the new window, locate Device Manager and click it. Expand the lists until you find your external HD, most likely with a symbol to the right of it (showing the driver is missing/out of date). Double click the external hard drive, go on the driver tab in the new window, and click update driver. When asked, select search for driver automatically and let windows do the work of reinstalling the driver for you.
Loud or any strange noise coming from the hard disk drive or external hard disk obviously indicates a hardware failure. Unfortunately, you cannot recover any important files on that storage device if it failed to function. The best thing you can do is to carefully determine if there is really problem with your external hard disk drive before concluding anything.