8G servers are not compatible with 2012 R2 ... not just not supported - not compatible. You can run 2012, but not R2. 2008 R2 is the ideal OS for this generation of server.
Trying to install Win Server 2012 R2 on my PowerEdge 1850.  I have the install on a bootable USB (created using Rufus).  The system boots and begins loading prep files for Windows installation and then I see the following:  [IMAGE]  I've tried recreating the USB on different drives and still receive this error.  I also tried turning the OS Install option in BIOS to Off.  When I do that, it goes to the Windows Logo but immediately fails and restarts.  Any ideas?
PowerEdge 1850 - Win Server 2012 R2 Install Issues