I am using docker toolbox on Windows 7 to run docker. (docker version 1.9.1)
As it turns out, the docker machine creates its VM at C:\\Users\\username\\.docker\\mach
I have had a bit of trouble with any of the solutions above but this is what worked for me:
MACHINE_STORAGE_PATH environment variable to point to your desired
directory/folder..docker directory..docker folder from the Users directory.start.sh script and added the line at the top:e.g.
export MACHINE_STORAGE_PATH=D:\\Docker