replacing failed hard drive

Thanks again. Your quick help reduced some stress and saved me some time.

WDC normally will provide a recertified drive. If the drive was just purchased, you might look at exchanging it with the seller.

Hi. Just an update. I put the drive in an external usb enclosure and connected the drive to my computer but it didn't show up in windows explorer so I checked the disk management area and I saw the drive listed there. It was divided up into 3 partitions which were labeled as healthy but disk management did not have any volume label associated with the partitions. I deleted the partitions in windows 7 disk management, which when doing so, I saw a message saying the partitions were not created by windows. Using disk management I formated the drive as one partition and ran windows checkdisk on it. It said the drive was ok so I downloaded the western digital program WinDlg.exe and ran a quick test on the hard drive and it passed. I guess I will put the drive aside for now and use WinDlg.exe to run an extended test on the drive overnight but I suspect the drive is ok. Perhaps there was some glitch with the ReadyNas unit. Maybe if I had shut down the ReadyNas without removing the second drive, then turned it back on again, it would have recognized the drive as ok, but at the time I didn't want to try anything on my own since I wanted to make sure I didn't make things worse. Anyway, I guess I won't know for sure if the drive is ok until I run the extended test on it. Thanks.

After running the extended test, it showed bad sectors, so I let it try to repair them but it couldn't. I bought the drives in May 2013, so I'll ask the store where I bought them if they can return it for me. I took a screenshot of the message saying the drive could not be repaired. I can print that out and give it to the store. Thanks for all the help.

Yes, if you can get a new drive from the reseller that's better. If you do an rma through wd you'll get a refurbished drive.