Not sure if you want to change the default machine folder to ~/.vagrant.d or VirtualBox.
If you want to move ~/.vagrant.d to another location. You can set the environment variable VAGRANT_HOME , see. This is https://stackoverflow.com/a/29304/ ...
Update:
To change the Machine Machine default folder VirtualBox, do it in the GUI => Prefs - General - Default Machine Folder or manually edit ~/.VirtualBox/VirtualBox.xml
<SystemProperties defaultMachineFolder="/path/to/VirtualBox/VMs" defaultHardDiskFormat="VDI" VRDEAuthLibrary="VBoxAuth" webServiceAuthLibrary="VBoxAuth" LogHistoryCount="3"/>
Terry Wang Jul 16 '13 at 22:54 on 2013-07-16 22:54
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