EHD not showing up, even in disk utility.

Hello there,

I'm sorry to be the bearer of the bad news but a scratching sound coming from an HDD is a really bad sign. Usually such sound would appear if the heads have crashed on the platters. Please stop any attempts to access the HDD as soon as possible. If the heads are still stuck on the platters they are causing more and more damage while you are trying to access the drive. This problem can often appear if you have dropped the HDD. If the data stored on the HDD is important to you consider using the services of a professional data recovery services. Have a look at the list of WD Data Recovery Partners here, most of them offer a discount for WD drives.

Restrain from using any testing or data recovery software on the drive as any intervention in such situation is likely to cause more damage and destroy even more of the data that's still intact.
You should also check the warranty status of the HDD and consider contacting the support team to arrange the RMA. If you decide to use DR services before replacing the HDD make sure that the service provider you use provides you with written verification, on its company letterhead, that it has performed data recovery on your hard drive, because any other unauthorized tampering with the HDD will void the warranty. Hope that helps.