It is very easy, you can simply move files and you are done.
Let me tell you step-by-step ..
Step 1.
Copy your whole c:\wamp\www folder to some safe place and then also copy your c:\wamp\bin\mysql\bin\data folder to some some safe place (path may vary a little).
Step 2..
Now uninstall current WAMP version and remove your c:\wamp directory.
Step 3.
Now install wamp again on some desired location, like D:\ with lots of space as you mentioned. When installation is complete, simply overwrite www with your backup and also mysql\data folder with your backup. You will find everything intact and back to place.
Goodluck !