Hyper-V cannot be installed: A hypervisor is already running.

If you want to add a Hyper-V Role on Windows Server 2012, under VMware ESXI 5.1, you may receive the error message “Hyper-V cannot be installed: A hypervisor is already running.”

To fix this you need to do the following:

1. First, shut down the Windows 2012 Server virtual machine on ESXI 5.1
2. Download and modify the .vmx file associated with your virtual machine, from ESXI server. 
3. Add the following lines to the end of the .vmx file:

·         hypervisor.cpuid.v0 = FALSE

·         mce.enable = TRUE

·         vhv.enable = TRUE

4. Upload the new .vmx file to ESXI Server
5. Restart your virtual machine.

Use the above at your own Risk.

VMware vSphere Hypervisor™ (ESXi) 5

VMware vSphere Hypervisor 5 is  the simplest and easiest way to get started with virtualization for free. This fully functional hypervisor lets you virtualize your servers and run your applications in virtual machines in a matter of minutes. vSphere Hypervisor 5 is based on VMware ESXi, the hypervisor architecture that sets the industry standard for reliability, performance, and ecosystem support. Consolidate your applications onto fewer servers and start saving money through reduced hardware, power, cooling, and administration costs.

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VMWARE-WDS

If you ever need to get VMWare Server 1.0.x to successfully connect to your Window Deployment Server (WDS) when you PXE boot into your WDS Boot WIM Image, then you need to add the following line to your config file for the virtual server;

Ethernet0.VirtualDev = "e1000"

It basically tells VMware to emulate an Intel adapter...