Is it possible to Install vCenter with only 1 windows server on the net?

I bought vSphere Essentials kit 5.1 and 1 copy of Win Server 2012 std. The problem is :

that

1. I cannot backup VMs without installing vCenter, but
2. vCenter MUST be installed on a Windows Server (DUMB!!! Why would you require a competitor's OS to do anything?). AND
3. vCenter requires Single Sign-On AND
4. SSO will not install on a Domain Controller. AND
5. Since I have only one server OS, it is a DC (as far as I can tell it either must be a DC or otherwise join an existing DC).

So it looks like I'm screwed. I have noticed some article about a new capability in win server 2012 that makes it OK to virtualize a DC, but I can find nothing saying I am licensed to do this without purchasing a new server OS.

Please tell me there is a way to fix this without buying something else!

thanks