simple use of a Windows OVA

test.json

{
    "variables":
    {
        "source_path": "",
        "output_directory": "",
        "vm_name": "",
        "username": "",
        "password": ""
    },
    "provisioners":
    [
        {
            "type": "powershell",
            "inline": ["dir c:\\"]
        }
    ],
    "builders":
    [
        {
            "type": "virtualbox-ovf",
            "communicator": "winrm",
            "source_path": "{{user `source_path`}}",
            "output_directory": "{{user `output_directory`}}",
            "vm_name": "{{user `vm_name`}}",
            "winrm_username": "{{user `username`}}",
            "winrm_password": "{{user `password`}}",
            "headless": "false",
            "shutdown_command": "shutdown /s /t 10 /f /d p:4:1 /c \"Packer Shutdown\""
        }
    ]
}

win10.json

{
    "source_path": "MSEdge - Win10.ova",
    "username": "IEUser",
    "password": "Passw0rd!",
    "vm_name": "win10-x86_64"
}