I've been working on a new internal portal for my employer using SharePoint 2010. As the project progressed, we experimented with several custom page layouts and, at length, settled on our two favorites.

With the decision final, we reassigned all the pages to the authorized page layouts and proceeded to delete the extras... all except one.

This page layout didn't want to get deleted. I was persistent, but the file was more so.

• Deleting the file in SharePoint Designer yielded the error "Server error: This item cannot be deleted because it is still referenced by other pages." Mind you, it wasn't, but SharePoint thought it was.
• Several online sources indicated that moving it to a sub-folder should allow deletion of the folder. However, in my case, doing so in SharePoint Designer yielded the error "Server error: This folder cannot be deleted because it contains the following page layout that is still in use: LayoutPage01.aspx."
• I could open the master page gallery in Windows Explorer, attempt to delete the file, or move it to a folder and delete the folder, and yet the file remained.
• I fired up PowerShell and attempted to delete the file with code, and received the same error.

Type                        : ItemDeleting
SequenceNumber              : 1000
Assembly                    : Microsoft.SharePoint.Publishing, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c
Class                       : Microsoft.SharePoint.Publishing.Internal.BlockDeletionOfInUseItemsEventReceiver

function Remove-PageLayout($siteUrl, $layoutName) {
  $site       = Get-SPSite $siteUrl
  $web        = $site.RootWeb
  $gallery    = $web.lists["Master Page Gallery"]
  $layoutItem = $gallery.Items |? { $_.Name -eq $layoutName }
  if(!$layoutItem) { throw (new-object IO.FileNotFoundException) }

  $layoutFile = $layoutItem.File

  $layoutFile.BackwardLinks |% {
    if(Test-Page $_.Url) {
      throw "Cannot delete page because it is referenced by $($_.Url)."
    }
  }

  $receiverType     = [Microsoft.SharePoint.Publishing.Internal.BlockDeletionOfInUseItemsEventReceiver]
  $unregisterMethod = $receiverType.GetMethod("Unregister", [reflection.bindingflags]"Static,NonPublic")
  $registerMethod   = $receiverType.GetMethod("RegisterIfNeeded", [reflection.bindingflags]"Static,NonPublic")

  $unregisterMethod.Invoke($null, $gallery)
  $layoutItem.Delete()
  $registerMethod.Invoke($null, $gallery)

  $site.Dispose();
}

function Test-Page($url) {

  $site = $web = $null

  trap [exception] {
    if($web) { $web.dispose() }
    if($site) { $site.dispose() }
    return $false
  }

  $site = new-object Microsoft.SharePoint.SPSite($url)
  $web = $site.openweb()

  $file = $web.GetFile($url)
  $result = $file.exists

  $web.dispose()
  $site.dispose()
  return $result
}