Create Hyper-V Virtual Machine from a .vhd file - powershell

Question

I'm trying to programmatically create a VM from a .vhd file - my code is below. I'm getting a weirdo file not found error, but I've TRIPLE checked all my paths.
ADD-VMHardDiskDrive : 'MyVM' failed to add device 'Virtual Hard Disk'. (Virtual machine ID C4A0BAFF-35EF-4B4C-9CA1-68D2ECF77BA1)
'MyVM': Attachment 'C:\temp\VMs\TheVhd.vhd' not found. Error: 'The system cannot find the file specified.' (0x80070002). (Virtual machine ID C4A0BAFF-35EF-4B4C-9CA1-68D2ECF77BA1)
My PowerShell code is:
$n = "MyVM";
$directory = "C:\temp\VMs"
$vhdxPath = "$directory\$n.vhdx";
$vhdPath = "$directory\Flash.480x800.vhd";
$vm = Get-VM $n;
if($vm -ne $null) { Remove-VM $n -Force; }
New-VM -Name $n -MemoryStartupBytes (Invoke-Expression "1000MB") -Path $directory;
Set-VMMemory -VMName $n -DynamicMemoryEnabled $true -MinimumBytes 512MB -MaximumBytes 4096MB -StartupBytes 2048MB -Buffer 20;
ADD-VMHardDiskDrive -VMName $n -Path $vhdPath;
Start-VM $n;
Any help is very much appreciated!!! Thanks!

Answer 1

I figured it out. The VM I was trying to attach was a "difference disk". I was missing the "master" disk that the reference disk was dependent on - hence the file not found error.
Thanks all.

Answer 2

In you code snippet, I guess you are assuming that ADD-VMHardDiskDrive would also "create" a VHD file for you. If that is the case, then we have root-caused the error. ADD-VMHardDiskDrive just adds a Virtual Hard Disk at indicated path to the VM. If the VHD does not already exist, that error is thrown.
If you want to create a new VHD or VHDX, use NEW-VHD commandlet before adding to the VM.
Alternatively, you can add an existing VHD to the VM or create a new VM as a part of New-VM commandlet itself. Take a look at the examples on technet:
http://technet.microsoft.com/en-us/library/hh848537.aspx