If your hard drive clicks it usually indicates a head is stuck and there is a means to fix this without replacing the head.Open the hard drive in a clean dust free area or as clean as can be made. (remember dust is a hard drive killer) there are 7 screws on a hard drive 6 around the edge and one hidden under the sticker. Once open if the head is on the discs the head is stuck as it should be parked on the head rail, what we want to do is move the disc counterclockwise by using a screw driver on the screw in the middle of the disk and slowly pulling the arm toward the the edge as we turn the disc and park it in the rail. Be very careful not to put downward or upward pressure on the the arm we don't want to touch the discs and make sure the discs are moving as you pull the arm. Once back in place put it back together and try it out . If it spins up and works move all your data off immediately. Its not fixed its probably going to stick again so move your stuff off right away. The other issue with a clicking drive can be that the head moves and bounces this does require a new head and your probably only going to get a new head from an old drive . You may be able to get a head on eBay or amazon but your best bet is to buy a similar drive on eBay and take it apart for the head.
Hope this helps and good luck
By the way do not touch the disks If you see any dust or anything on the disk blow on it DON'T TOUCH IT. If it doesn't blow off when the disc spins up it will throw anything off the platter . JUST DON'T TOUCH