There's a great tutorial on WeGotServed  for owners of the HP MediaSmart Server who want to upgrade it to WS 2012 Essentials.

We are shown how to make up a VGA cable so we can access the bios on the MediaSmart Server, and then taken through the process of installing WS 2012 Essentials onto the box:

Overall my whole journey from Windows Home Server v1 to Windows Server 2012 Essentials with the HP EX470 has been joyful. Now don't get me wrong, it has been emotional - having to quickly learn how to make the infamous VGA cable, hurting my fingers during the assembly and spending a good while trying to figure out why the EX470 wouldn't boot from the USB thumb drive. But the end results are incredible. Let me say that with 2GB RAM and a dual core CPU, Windows Server 2012 Essentials runs beautifully.

You can find this tutorial for HP MediaSmart owners here.

Installing WS2012 Essentials on the HP MediaSmart Server is a post from: MS Windows Home Server - Your Personal Guide to Microsoft Windows Home Server!