Hyper-V orphaned or unnecceasry file script

This code is just a general idea and you will need to modify it to meet your needs, but in short, you basically need to. . .
Get the location where Hyper-V is setup to store VHD and VHDX files
You need to collect the full path name of each of those files
You then need to query each VM for each of it's hard disks and get the full path name to those files as well
You then need a method to compare those 2 collections of objects to one another and see which one is "not accounted for"
DO NOT DELETE FILES WITHOUT CONFIRMING IT IS SAFE

$VirtualHardDiskPath = Get-VMHost | Select-Object -ExpandProperty VirtualHardDiskPath
$FilesInUse = Get-VM | Select-Object -ExpandProperty HardDrives | Select-Object -ExpandProperty Path
$Allfiles = Get-ChildItem $VirtualHardDiskPath -Recurse | Select-Object -ExpandProperty FullName
$PotentialOrphan = Compare-Object -ReferenceObject $Allfiles -DifferenceObject $FilesInUse -IncludeEqual -PassThru | Where-Object {$_.SideIndicator -eq "<="}
Write-Warning -Message "The $PotentialOrphan file may be an orphaned file"

This is just a starting point. You would also need to consider whether or not the Hyper-V server is in a cluster. if so make the script run so that it checks all of the nodes in the cluster.

You would first need to determine if the Hypervisor(s) are clustered or stand alone servers.
You would need to capture the default VM storage location from Hyper-V itself
You would need to do a recursive file search at that location for any files that might be VHD or VHDX files
Then for each of those files check every VM to see if that is attached as a drive
If no VM is using the file have the script do whatever you need to do. In my example I just have it write a warning that the drive is potentially orphaned. You need to manually be sure before you assume or delete any files but this script will at least show you files that are not attached to any VM.

Function Get-OrphanedVHD
{
Param ([Parameter(Mandatory=$true,Position=0)]$ComputerName)
$VirtualHardDiskPath = Get-VMHost -ComputerName $ComputerName | Select-Object -ExpandProperty VirtualHardDiskPath
$Files = Invoke-Command -ComputerName $ComputerName {Get-Childitem -Path $VirtualHardDiskPath -Recurse | Select-Object -ExpandProperty FullName}
foreach ($File in $Files)
    {
    $VMPath = Get-VM -ComputerName $ComputerName | ForEach-Object {Get-VHD -VMId $_.VMId -ComputerName $ComputerName | Where-Object {$_.Path -like $File}}
    if ($VMPath) {Write-Verbose -Message "$VMPath is currently attached to a VM"}
    else {Write-Warning -Message "The $File file is potentially an 'orphan'"}
    }
}
$Nodes = Get-ClusterNode | Select-Object -ExpandProperty Name
if ($Nodes)
    {
    foreach ($Node in $Nodes)
        {
        Get-OrphanedVHD -ComputerName $Node        
        }
    }
else
    {
    Get-OrphanedVHD -ComputerName $ENV:COMPUTERNAME | Select-Object -ExpandProperty VirtualHardDiskPath
    }

You should also be concerned with orphaned checkpoints or snapshots. When I used to work with Hyper-V a lot more I had written a lot of scripts to do just this kind of maintenance. I don't currently have access to those files right now so I rewrote this from scratch ion kind of a hurry, so it should at least give you a starting point.

The backup software we used to use could sometimes leave orphaned checkpoints. it would be extremely difficult to delete them is the "chain" is missing a link. The checkpoints can not simply be merged unless all the files are there. So be careful about deleting things. Make sure no VMs have checkpoints before you proceed at your own risk!