After previously spending several hours trying to resolve the issue myself...An hour on the phone with AppleCare...Another 3o minutes in an Apple store (where I'd toted my laptop, hard drive, and AEBS) with a "genius"...I finally managed to get my 500GB WD external Hard Drive hooked up to my AEBS and visible and accessible to my laptop running Windows 7 (just upgraded from Vista).
First, the bottom line....AEBS definitely does NOT work with NTFS. I tried every trick I could think of but it was all to no avail. Ultimately I reformatted my hard drive to be FAT32 rather than NTFS by hooking it up directly to my laptop and running a utility called "fat32format" which you can find at this lnk"
http://www.ridgecrop.demon.co.uk/index.htm?fat32format.htm.
Several people have noted the usual limits imposed by Windows on a FAT32 formatted drive but I was able to successfully format my 500GB drive with the tool above without issue. Once I did that I hooked it up to my AEBS and by the time I got back to my laptop (my router's in another room) I had a pop-up window on my screen notifying me of the newly available drive on my network. Such a beautiful thing!!!
I hope this post helps some of you folks avoid the degree of frustration I experienced while trying to get my AEBS and external hard drive to play nicely together!