I have a Dell PowerVault NX3200 that has a product key for Windows Storage Server 2012 on it. I need the installation media as the OS is gone. Upon calling Microsoft they told me Dell would have to provide it but Dell would not give me anything since the machine is out of warranty. I have a perfectly good product key but no way to install the operating system and no .ISO. 

How can i get a Windows Storage Server 2012 ISO? I tried installing the evaluation version from Microsoft but it wouldn't let me upgrade to the standard version with my product key. The product key was verified as valid by Microsoft. Would it only work on the Workstation version of WSS2012?