I am trying to create a virtual machine based on Windows Server 2012 R2 ISO file inside Hyper-V.
I create the VM and chose add "Connect a virtual harddisk later". I started the VM and went to Media and clicked on set in a disk and chose Win 2012 ISO file. It started installing Windows 2012, I entered product key and chose server with GUI. when it comes to choose which type of installation do you want, I chose Custom and clicked next. Now I cannot find any device to install the windows server 2012. I click on load driver and "select the driver to install" but it is empty. I click on Browse what ever I choose it says "No signed device drivers were found. Make sure that the installation media contains the correct drivers, and then click ok". I can assure that the iso file is not corrupt.
You do need to create a virtual hard drive to install Windows. Here are instructions for creating a Windows VM with Hyper-V complete with installing from an ISO.