Frees the specified private data associated with this volume.
HRESULT FreePrivateData( REFGUID refguid );
If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be one of the following: D3DERR_INVALIDCALL, D3DERR_NOTFOUND.
Direct3D calls this method automatically when a volume is released.
Header: Declared in D3d9.h.
IDirect3DVolume9::GetPrivateData, IDirect3DVolume9::SetPrivateData