Microsoft offers 180 day fully functional trial of Windows Server 2012. You can install it on a standalone PC with a 64 bit CPU, or you can set it up as a virtual machine.
I have installed it under VirtualBox running on MacBook Pro. Setup went smoothly and was completed with very little user input.. If you are using VirtualBox, don’t forget to install guest additions after Windows has been set up. My virtual machine has 35GB disk and 2GB RAM, and I haven’t noticed any performance issues.
Downloadable ISO contains Windows Server 2013 standard and datacenter editions. When installing, select to install version with GUI (user interface).