One of the earliest scripts I wrote and felt confident enough to publish on my blog at http://ben.neise.co.uk/index.php/2009/03/vm-object-dns-name-mismatches.

VMAndGuestNameMismatchFinder.ps1

# Get all of the VMs as an object
$objVMs = Get-VM
# Loop through all of the VMs
ForEach ($objVM in $objVMs){
  # Get the VM Guest object (which contains the DNS information)
  $objGuest = Get-VMGuest -VM $objVM
  # Set a variable to the VM object name
  $objVMName = $objVM.Name
  # Set a variable to the DNS name
  $objVMFQDN = $objGuest.Hostname
  # Sometimes the FQDN is empty or blank, so we screen those out with an "If not equals"
  If (($objVMFQDN -ne "") -and ($objVMFQDN -ne $null)){
    # The host name is the first part of the FQDN, so we split it, and take the first (0) segment as our host name
    $objVMHostName = $objVMFQDN.split('.')[0]
  }
  Else {
    $objVMHostName = $null
  }
  # Check that the host name is not null, and if the hostname does not match the VM name, echo the results
  If (($objVMHostName -ne $null) -and ($objVMName -notlike $objVMHostName)){
    # Write the results on one line, the VM object name, then the host name in square brackets.  The "`" is an escape character
    Write-Host $objVMName `[$objVMHostName`]
  }
}