Totally the wrong forum for that question. However, when you installed Windows you had the option to partition the hard disk which would have allowed you to create a smaller C: drive for Windows and the remaining free space could be used for D:. If you
don't want to reinstall, try disk partitioning software - try the free version of EaseUS at www.easeus.com which works well.
Phil P.S. If you find my comment helpful or if it answers your question, please mark it as such.