It is my fault to attach it without checking but I did install the latest firmware before attaching the drive.
It looks like the router changed the settings of the HD - is there a way to put the original settings back? I have not written to the drive so I hope the data is still there on it.
I too got a bit “hasty” and attempted to connect a WD My Book Essential 3TB drive to my Linksys E4200 about 2 weeks ago. I had checked the “compatibility chart” and did not find the drive listed but then I figured that since it was a new drive there might not have been enough results compiled yet to publish the results. Prior to connecting the drive, I made sure I had the latest firmware levels on both my drive and my router. I got the same results as the previous commenter. The router saw only 768GB of the 3TB drive and when I disconnected from the router and connected to my pc an error message appeared that said the data was corrupted and I needed to reformat. I attempted to reformat the drive (losing 1.7TB of “copied” data) but I was also surprised to find that I was only presented with a 768GB partition in my disk utility window. My recovery efforts to reformat back to a 3TB partition were in vain so I took the drive back to the store where I had purchased it and replaced it. I like both the drive and the router but did not have a good experience with the marriage of these devices. Hopefully a new router firmware update will alleviate this incompatibily soon.