Makes slow click sound but not read by the PC

Any sounds other than a light humming or hearing that arm move lightly back and forth is usually a sign of the hard drive failure beginning.

Does the computer have a S.M.A.R.T.S. system on it in the bios. What model of computer is it? You need to get in the bios by tapping F10 or DEL key a few times when it shows the first screen on the monitor.
Once you get in bios, go through each tab and see if you can locate a smarts option and make sure it is enabled.

Scandisk is only good if there is actually bad sectors or bad headers on the platters of a hard drive, corrupt data and such, thus it gives you the software physical side of the hard drive, but the smarts is a self monitoring system. It detects abnormality in the hard drive itself and warns you ahead of time of a catastrophic failure due to the way the drive is not acting correctly.

Here is more info about smarts. Hope this helps.
What Is Drive eHow

Sounds like your drive has died; check this out to confirm;
http://www.lifehack.org/articles/technology/how-to-tell-when-your-hard-drive-is-going-to-fail.html

It sounds like you have damaged the drive.

The clicking sound is a mechanical failure where the the read arm inside the drive is hitting the magnetic platters. You should backup your data immediately as drive failure is imminent.

Robert from Blitware

The click comes from the reading head of the hdd, the beep comes from the pc when encounters an error. If the power source of the hdd hasn't been specifically designed to support both voltages, when you plugged it in for the first time it fried. It and all the data on it are gone.

If you are running Vista, You might be one of many people who are reporting an update that is causing some buggy behavior. Try this:

Connect the drive but do not Format the drive, right click 'my computer' then 'manage' go to 'storage/disk management' view the drives; your usb drive will not be allocated a drive letter. You can set one manually or leave it for about 2~5 minutes for one to be allocated auto. Each time you connect the drive you may have to do this.

Here is the support website for the LACIE products.  As far as I knowthis site simply answers questions. Sounds like the hard drives are bad to me. 
http://www.lacie.com/support/

You're not missing any step at all, because with SATA hard drive if its really working your computer should
automatically detect it and since this hard drive suddenly stop working there's a possibility that its already
fried but if you want you can try this hard drive again to a different computer and if still not detected by
second computer its already dead.........

A power supply failure can cause this; I've just been through it myself. If you have access to another LaCie drive, try its power supply on the "failed" one and see if it works.

Ok! This is bad, just like any HD when you start hearing noises clicking, vibrations, it is due to a loose or faulty cylinder. These things are not worth the repair and your files are lost. The only thing that you can do is try to hook this up to another PC to see if it will work long enought to extract the files. Keep in mind a lot of companies manufacture these devices, but there largest business is geared towards Microsoft customers, so if you have a Mac do not count on guarantees for these devices to function properly with your unit.

A clicking noise from a harddrive is defenenly NOT a good thing. It usually means that the harddrive is going bad.