Broomie--
Sure there is! Go to your default "audio" view. Does one of the columns you have there say "Filename"? You need to see the entire path, from "C:\" to ".wav". If you don't have a "filename" column, add it by right-clicking/customize current view.
Go to your "filename" column and start by selecting ONE track (we'll start with only one). When you're in the "filename " column, right-click/library tools/find and replace. You want to FIND "c:\" and replace with "d:\". Once the name is changed, you should see the icon for a file present, and should be able to play it. Try playing it to be sure.
If one works, try ten, then a hundred, then let fly with your whole library. This operation is easy to mess up (I have), but easy to recover from also.
Here's a tip: If you have files you haven't moved yet, you can do that totally within MC. Right click/library tools/rename from properties. Here you can rename a batch of tracks to d:\<artist>\<album>\<track>, etc etc etc.