Update vti_author in SPDocumentLibrary item using PowerShell?

Question

I want to update the property vti_author in an item in a SPDocumentLibrary, but it doesn't work. The items original vti_author is the same even after running this script, why?

$spSite = Get-SPSite http://mySite/
$spWeb = $spSite.OpenWeb("News");
$spDocumentLibrary = $spWeb.Lists["Pages"];
$items = $spDocumentLibrary.GetItems();

foreach ($item in $items)
{
    $vtiAuthor = $item.properties["vti_author"];

    if ($vtiAuthor.EndsWith("sp_reader"))
    {

        # Check out 
        $file = $item.File; 
        $file.CheckOut(); 

        # fails - no read only field
        #$item.properties["vti_author"].ReadOnlyField = false;

        $newAuthor = "DOMAIN\user"; 
        $item.properties["vti_author"] = $newAuthor;  
        $item.UpdateOverwriteVersion(); 

        # Check in 
        $file.CheckIn("Updated by System");
    }
}

Answer 1

As suggested here: http://social.msdn.microsoft.com/Forums/en-US/sharepointdevelopment/thread/1f42e45e-160f-457d-b4dd-cb228e49abb7

You should use following fields along with UpdateOverwriteVersion() method to update fields such as author, date created etc.

// The actual User Information is within this SPListItem 
                    SPListItem userItem = documentList.Items.GetItemById(1);                   
                    userItem["Created By"] = currentWeb.EnsureUser("user").ID; 
                    userItem["Modified By"] = userItem["Modified By"]; 
                    userItem["Created"] = DateTime.Now.AddYears(-3); 
                    userItem["Modified"] = DateTime.Parse("01/01/2000");
                    userItem.UpdateOverwriteVersion();