Starts a VirtualBox Virtual Machine with the maximum possible number of virtual monitors.

StartVMWithMaxMonitors.ps1

# Starts the specified VirtualBox virtual machine with the maximum number
# of virtual monitors (i.e. with the number of virtual monitors matching the
# number of physical monitors attached to the PC).

# Set these variables as appropriate for your environment.
$virtualboxBinFolder = "C:\Program Files\Oracle\VirtualBox"
$VMName = "MyVirtualMachine"

# Returns the physical monitor count for this PC.
Function GetMonitorCount
{
    # See http://stackoverflow.com/questions/7967699/get-screen-resolution-using-wmi-powershell-in-windows-7
    Add-Type -AssemblyName System.Windows.Forms
    $allScreens =  [System.Windows.Forms.Screen]::AllScreens

    return $allScreens.Length
}

# Sets the virtual monitor count on the specified VirtualBox virtual machine,
# and then starts the machine.
# Assumes the $virtualboxBinFolder global variable points to VirtualBox's bin folder.
Function StartVMWithMonitorCount ($VMName, $monitorCount)
{
    & "$virtualboxBinFolder\VBoxManage" modifyvm $VMName --monitorcount $monitorCount
    & "$virtualboxBinFolder\VBoxManage" startvm $VMName
}

StartVMWithMonitorCount $VMName (GetMonitorCount)