You could move the game folder to D:Game and create a symlink that points from C:Game to D:Game. This sort of trick allows you to move your installed programs and games without much trouble. Symbolic links (or “symlinks”) will allow you to move a directory while “tricking” Windows into thinking it’s at its original location.
You’ll either need to uninstall and reinstall the program to the new location, or use symbolic links. However, most programs will display errors if you attempt to drag and drop their folder to a new location. Some programs can be moved easily-for example, you can just move your entire Steam folder to a new drive and run the Steam.exe file to launch it. Moving programs after the fact is often more difficult.
Adding new folder locations for game installations is dead simple in Steam-just open Steam’s Settings, select Downloads, click the Steam Library Folders button, and add a new folder on a different drive.
