You can move or copy your files to the new hard drive but that will sever the connection to LR and you'll have to "reconnect" them. This is easy for a a few folders but I've never done it for a whole catalog. I'm sure someone with the Xmas spirit on this forum will cite you to the best method or you can search for one of the old threads on this forum.
There are two ways to do this.
But first create one parent folder on your D drive (call it "Images" or whatever you like) by clicking on the "+" sign besides the header <Folders> in the folders panel (left side in Library).
Then do either one of the following:
a) In LR drag and drop your folders containing your images into the new created folder on drive D. I don't know if you can move the <My Pictures> folder as such since it is a feature of <My documents>. If you do the move in LR you don't have to do anything else because LR will keep track of the changed location.
b) Alternatively you can do the move of your images in your OS (Win Explorer) but you then have to re-link LR to the new location of your images. If you choose this method it would be best if you first create a new parent folder for all your image folders. That means that in LR you create a new folder in <My Pictures> - call it "Images" - and drag-and drop all your image folders in this new parent folder. You do all of this in LR. so that LR "knows" that the folder structure has been changed. Then in Win Explorer move (not copy!!) your newly created parent folder from drive C to drive D.In Win Explorer you highlight this folder and then go >Edit > Move to folder. WARNING: Do not change the folder structure at this point, and do not make any changes to the names of image files or folders.
After this has been done you have to re-link LR to the new location of your images. You will see in LR that the image folders will have question marks besides them. That is expected. Right-click you parent folder that you created in LR in the first step and select <Find missing folder>. Navigate to your drive D and click on the corresponding folder. LR will then find all the sub-folders within this parent folder on its own, provided you have not changed the folder structure and/or folder names outside of LR.