HDD will not disconnect, causes issues shutting down

Hi, I have a Western Digital external HDD (1 TB) that I use to store all my media (connects via ESATA and USB 2.0, but I have never used the USB connection, and unfortunately I have no idea where it is). I recently tried reconnecting the HDD to my laptop, but for some reason it reconnected with a different drive letter than usual. So I tried changing the drive letter, but I received an error (some ambiguous error saying the action couldn't be completed, likely because something was accessing the drive). So I disconnected the drive, but now, any time I reconnect it, my computer doesn't fully register the drive (it appears in My Computer without the available space information, and any attempt to access it doesn't work). On top of that, certain programs hang up and don't run (such as the Virtual Disk Manager and Hardware Manager for removing it safely). I am also unable to shutdown the computer while it is "connected", it hangs up at the Shutting Down screen, and nothing happens (I waited 8 hours over night, it shouldn't take that long), so I have to force a shutdown.

The real kicker is that if I simply unplug the device, nothing happens. All the problems persist as if the drive is still there (it even shows up in device manager), including being unable to shutdown. If it isn't connected, my computer operates perfectly fine.

I am completely baffled here. I'm normally perfectly capable of solving any computer problems on my own (this is my first time posting for computer help), but I have never seen anything like this before, and have found nothing online.

Any ideas? I really appreciate any help/advice. Let me know if there is any other relevant info I should post.

Yeah, that's what I thought too, but the reason I tried changing it in the first place was because I couldn't access my music through the Zune software. The music library was still mapped under G:, but it wasn't being found, so I checked my HDD and saw that it was now the J: drive, so that's why I tried changing it.

Also, I already tried seeing if I could change the letter again, but the problem is that it is normally done through Disk Management, but that hangs up while it is trying to connect to the Virtual Disk Service. As a result, I am unable to do ANYTHING through disk management.

Like I said, I'm kind of baffled on this one, all the usual solutions (or at least what I initially thought would work) don't seem to be the solutions to this problem.

Just to make sure I'm clear, this isn't a Western Digital portable hard drive (like the My Books) that only operate on USB. It's a "regular" hard drive that I put inside of an external casing (hence why I am able to use ESATA).

It's fixed! I'll explain what I did below in case anyone reads this who has a similar problem:

So I connected the hard drive and ran the scan, and it froze at %46. So I shut down the computer (just did a hard shut down, without using the menu since I knew it would freeze anyway) without turning off or disconnecting the hard drive, which is something I hadn't done before.

After I started the computer back up, first thing I did after logging in was run the checker, didn't bother to check the status of the hard drive (in retrospect, I probably should have since I did something new). After the scan finished, it reported finding no errors on the drive, so I checked it out in Disk Management and My Computer, and everything was working properly! So I'm not sure what portion of the above process fixed it, but something did. I hope it was the scan that did it, despite not reporting any problems, since the other portion of the process seems like a horrible solution to the issue.

Regardless, thank you so much for your help!