#requires -version 2.0

param (
    [Parameter(
     ValueFromPipeline=$false,
     Position=0,
     Mandatory=$True,
     HelpMessage="Enter a service name like spooler.")] 
     [String]$service,
     
     [Parameter(
     ValueFromPipeline=$false,
     Position=1,
     Mandatory=$false,
     HelpMessage="Enter a computername. The default is the local computer.")] 
     [String]$computername=$env:computername
     )

#make sure you run this in an elevated PowerShell session

function Get-Required {
#requires -version 2.0
  Param([string]$name,[string]$computername)
  
  $errorActionPreference="SilentlyContinue"
  
  Get-Service -Name $name -computername $computername -requiredServices  | foreach {
  #write the service name to the pipeline
   write $_
   Get-Required $_.name $computername
   #filter out duplicates based on displayname
  } | select displayname -unique | foreach {
  #then get the re-get the service object
   Get-Service -DisplayName $_.displayname -computername $computername
  }
  
 } #end function  

#main script body  
try {
 Get-Service -Name $service -computername $computername -ea stop | Out-Null
 Get-Required $service $computername 
}
catch {
 Write-Warning "Failed to find service $service on $computername"
}
Finally {}