I connected this display to a Thinkpad T40 yesterday. The Displays cable has USB, which is all you need to connect to your PC. At first we got nothing, then we got only the screensaver on the Display and the open program on the Thinkpad. Then the cursor went from one screen to the other for no apparent reason. I couldn't find any driver or anything to help. We turned things on/off, rebooted a couple of times. This morning my wife used the Thinkpad for a while with the Display turned off, then put the Thinkpad on suspend. When I took it off suspend by pressing the button on the port replicator with the cover down, the display started working perfectly.
If this sounds confusing, it is. The upshot is that you don't need another cable. You do need the right video card (there's some information on apple.com/support/displays. You can go to your video card's manufacturer's website to see its specifications and match it up to the Display's as best you can.
Our experience is to play with it a little, without doing anything really other than turn on and off a few times and suddenly it works.
Good luck!