|Davidsd you can not create a new partition unless there is raw space to make it in. So where did the raw space for d: come from?|
Only conclusion I can come to is you would have to "shrink" your c: partition to make space available for a d: partition.
You would have done something like this:
You did not delete an existing partition like a utility partition and then turn this into d:? Otherwise please explain how you got the free space to make d:.
Also what OS were you trying to install on d:?