Hi Jetjock,
I'm Rodrigo and I'll help you.
You can move your user shell folders to D: (Music, Pictures, Downloads, Documents, Desktop). Create the respective folders on D:, you can use any folder structure you want. Right-click the User shell folder (e.g.: Documents) > Properties > Location tab > Move... > Select the folder you created on D: (do not select D;, always the folder you create inside D:). You will be prompted to move the files to the new location you selected, select "Yes" to move or "No" and you can move the files later.
Repeat the process with the other folders.
About "Program Files", most programs allow you to select where you want to install it, to make them work correctly, you need to reinstall selecting to be installed on D:, some programs do not allow it because they require to be installed on C:/
These options will free a lot of space on C: