Powershell Script to identify users with the same display name

Like that, for example:

$duplicates = @{}
Get-ADUser -Filter "DisplayName -like '*'" -ResultSetSize $null -Property DisplayName | ForEach-Object {
	If (-not $duplicates.ContainsKey($_.DisplayName)) {
		$duplicates[$_.DisplayName] = @()
	}
	$duplicates[$_.DisplayName] += $_.SamAccountName
}
$duplicates.GetEnumerator() |
	Where-Object {$_.Value.Count -gt 1} |
	Select-Object -Property @{n='DisplayName'; e={$_.Name}}, @{n='Used by SamAccountNames'; e={$_.Value -join ', '}} |
	Export-Csv -NoTypeInformation -Path "C:\Temp\Duplicates.csv"

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Thanks for that.  Could I just copy that directly into a .BAT file to run from the Active Directory server?

That's PowerShell, so it's .ps1. Otherwise yes, save it as it is.

Thanks.  Done that but how do I enforce it to run on the server as administrator?  Currently when I open the file with PowerShell it runs but I don’t see the output CSV file.

As usual: you right-click the PowerShell shortcut and choose "Run as administrator". These are just read operations, so unless you explicitly restricted access, a regular user should be able to run it as well.
If it doesn't produce output (no error messages either?), then there probably aren't any duplicates.
Setup a test user with a known duplicate DisplayName and run it again.

Thanks for you help.  It is giving a red error but it flages on the screen and is too quick to read.

Perfect!  Much appreciated, all now working.  :)