Hi.
You can choose where to install the content when running the installer. This option is not so obvious but it is there.
You can try to manually move the vst sound files of the Grand from C drive. Next time you run it you will get error message saying the files are missing. Click Locate, and point it to the location where you moved the files. It will create shortcuts in the original file location pointing to where the files actually are.
But ideally you should select a location for the content when installing.