I'm trying to extend my D: partition in Windows Vista Home Premium to contain the 30.91 GB unallocated space seen below:

I've read this thread which says it is not possible to extend "backwards", and the answer to it says I should use third-party tools.
I was under the impression that third-party tools use the system commands anyway.
How can I extend the unallocated space into my D: drive without third-party tools?
