Zend certified PHP/Magento developer

Is it wise/possible to Extend C: on a Single 1TB Partitioned Drive?

I have a production computer at work that is running 2x 1TB Drives in RAID1
The person who partitioned the drive did so very horribly.

The computer is running Windows XP
C: 40GB
D: 850GB

There is no Unallocated Space anywhere.

Is it possible to somehow shrink the D: and make Unallocated space and attach that to the C:?

It seems like if it is possible the Unallocated space would end up after the D: so I would have to Allocate enough space to move the contents of the D: to the new drive (E:) and then delete the D: and then I would be able to Extend the C: with the unallocated space from the D:?

Then I would have to re-create the D: and move everything back.

Does this sound correct?
Is there a better way to do this or is it even possible?
Is it wise to do?

Even if I cloned the drive to a 2TB drive the Unallocated sectors would still end up at the end and I couldn’t extend the C: could I?

Thank you for your time and help on this.

Kind regards.