Based on what was said you can also proceed as follows:
1. Shrink the D partition with Disk Management
2. Image the shrunk D partition. Easiest is to use Free Macrium
3. Delete the D partition so that you get unallocated space
4. Extend the C partition by the amount that D was shrunk - but not more, rather use a little less. Reason: If you use more than the shrunk amount, the image will not fit in step 6.
5. Create a new D partition from the remainder of the unallocated space - this can be done with Disk Management.
6. Restore the image of D into this new D partition.
I would prefer this solution because you only need Disk Management to manipulate the partitions - and Disk Management is safe. Partition Wizard is a nice program which I use a lot, but for the uninitiated it is easy to make a mistake and to muck up all partitions on that disk (has happened to me in the beginning too).