A: The correct PowerShell cmdlet to use to add a virtual hard disk (VHD) to an existing virtual machine (VM) in Windows Server 2012 is the Add-VMHardDiskDrive cmdlet.

Here's an example showing its use on IDE:

<code>Add-VMHardDiskDrive -VMName <vm name>-ControllerType IDE -ControllerNumber 0 –Path "<vhd path and name>" -ComputerName <server></code>