I recommend using
MiniTool's parition wizard which is free and awesomely easy to use.
You will need some free unallocated space (not belonging to any partition) right after the C:\ partition.. that's between the C:\ and the D:\ partitions.
To summarize, here are the steps:
1- Free some space from the end of the D:\ partition. (Shrink your D :lol
2- Drag the D:\ partition to the right of the free space, so that the free space will be before it, not after it.
3- Expand your C:\ partition, so the free space will be at its end.
You could also check their
guide for pictures.
Note: It could take some time to move the free space from AFTER to BEFORE the D:\ partition.