Its good to have a small C drive, put games and other softwares in D drive, by default your computer will always seleect C, you can always select any other drives to install softwares or store data files.
The reason for the small C drive is incase Of Virus attack or system crashes warranting reinstalling of Operating System it might be possible to save important data on other drives while only deleting data on C drive. You can always use short cuts on desktop screen while keeping the main files in D drive.