Try this:
 Code:
$objComputer = GetObject("WinNT://"+@WKSTA)
$arrFilter[0] = "User"
$objComputer.Filter = $arrFilter
For Each $objUser in $objComputer
  ? $objUser.Name
  if $objUser.Name = "unwanted"
    ? "Unwanted User detected, trying to delete..."
    $objUser.Delete
  EndIf
Next