Clicking drive almost always equals failure. I've gotten a few of them going long enough to preform a ghost to another drive, but it's difficult to do.
Pull the drive out, hook another one up to it that you can ghost to, and make sure you have a bootable floppy and a copy of ghost on a flopy. When you power on the system, hold the drive at different angles each time. I've gotten them to work flipping them over, setting them sideways, etc. When and if it does show up in the POST, DO NOT MOVE IT!! Get into ghost and clone that failing drive. It helps to have someone there, and make sure you're comfortable. Cause if youre holding the drive at an angle that makes it impossible to prop it up, you might be there a while.
Before you attempt the ghost, you might want to call the drive manufacture and get an RMA. Ask them to cross ship a new one to you. They'll need a credit card number, but it won't be charged. If they ask for an error code, tell them it's clicking and will not POST. You should have the new one in a couple days (WD sends them airborne express) and you can attempt a ghost to that one if you have no other drive. (this will only work if the drive is <3yrs old)
Good luck.