WD20EARX in enclosure not showing

I’m trying to use a WD20EARX with an external enclosure for backup.  The enclosures I’ve tried using are a Thermaltake Max 5 and a Rosewill RX-358.  Both are supposed to accept up to a 3TB drive, and I’ve successfully used both with a Seagate 2TB Barracuda LP, equivalent to the Caviar Green.  

In Windows 7, when I plug the drive in via USB, Windows recognized the drive as a “USB mass storage device” in the device manager and says it is working properly.  Yet I cannot see a drive in Disk Management to format and assign a drive letter.  I also hooked up the drive to a Macbook Pro using OSX Snow Leopard and the system also couldn’t see it.  I even plugged it into a Windows XP Pro machine to see if it was a driver issue with Windows, but XP did the same as Windows 7, the only difference was that XP could tell me that it was a WD20EARX in the device manager properties for the USB storage device.  Win7 provides no information other than it is “working properly”.

I do not have a desktop anymore to hook the drive up to, but the enclosures are working fine with the Seagate.  The fact both Windows and the Mac cannot see the drive is leading me to think the drive is DOA.  Unfortunately I held on to it too long to return to the retailer.  Does anyone have a suggest for something else to try?  

The easies way would be to find a desktop computer and connect the hard drive directly to the computer motherboard. That way you can know if it is a compatibility problem with the enclosure or not. Usually with a new hard drive you need to initialize it first, check the link for the steps.

http://wdc.custhelp.com/app/answers/detail/a_id/1018/session/L3RpbWUvMTMyODM1Nzg0Ni9zaWQvR0xBU3lSUGs%3D  

The problem is the disc won’t even show in disk management.  There is nothing to initialize.  I don’t anyone I know still has a desktop to test this thing on.  The only desktop I have doesn’t even use SATA, it is a relic. 

Let me ask this.  Is anyone else using a WD20EARX with an enclosure?  If there is one that is not too expensive, I’d just buy it to test it.  It might be easier than dealing with the RMA process.