Unable to install DHCP server, not enough disk space

Despite having over 3GB of available space, I am unable to install the DHCP server role.

This originally was a 10gb virtual box drive image, but when I ran into space issues extended the drive to 12gb. I've subsequently run chkdsk and defrag, to see if I could get Windows to recognize the available space.

Is there some way I can convince Windows Server 2012 I have enough disk space?

From TechNet on the absolute minimum requirements to run Server 2012 R2:

Be aware that 32 GB should be considered an absolute minimum value for successful installation. This minimum should allow you to install Windows Server 2012 R2 in Server Core mode, with the Web Services (IIS) server role. A server in Server Core mode is about 4 GB smaller than the same server in Server with a GUI mode. For the smallest possible installation footprint, start with a Server Core installation and then completely remove any server roles or features you do not need by using Features on Demand. For more information about Server Core and Minimal Server Interface modes, see Windows Server Installation Options.