Can't create new tablespace for PostgreSQL data. Permissions denied
For some reason I don't seem to be allowed to change my PostgreSQL data folder to a drive other than the C drive.


This is not the correct way to do that anyway.  Creating a tablespace and moving the whole cluster are different things.


  I am an admin on that machine and I have made sure that I have 'full control' on the D drive.


It doesn't matter who you are, what matters is who is the service account running PostgreSQL, and what permissions that account has.