dll.xml Information and Troubleshooting


Several addons corrupt the FSX dll.xml file, which can render inoperative any addon that relies on dlls loaded from it.  Numerous attempts at getting these developers to fix this issue have gone unanswered.

At its most basic level with no actual addon dlls loading, the dll.xml file looks like this:
<?xml version="1.0" encoding="windows-1252"?>
<SimBase.Document Type="Launch" version="1,0">

Actual entries for loading dlls look like this and are placed after the Launch.ManualLoad tags but before the ending SimBase.Document tag in the basic structure shown above:
  <Name>PMDG HUD Interface</Name>

Most of a dll.xml is made of up a succession of these entries that tell the sim to load particular addon dlls.


The dll.xml file is normally located in a hidden location.  Here's how to find it.
  1. First you need to open the Windows Folder Options.  You can get to this either from Control Panel, or by going to Tools/Folder Options from any Explorer window that shows your drives and folders such as My Computer.
  2. In the Folder Options, you need to change two options on the View tab away from their default settings:
    1. The first is "Hidden files and folders" - you need to change this to the 2nd option down that says "Show hidden files, folders, and drives."
    2. The second is "Hide extensions for known file types" - uncheck this option.  Extensions are the second half a filename, for example .doc, .jpg, .mp3, or in this case .xml.  For some reason, Microsoft decided to hide these by default, which can make it difficult to identify the exact files in a list.
  3. Now, you need to browse your main C: drive, and go to one of these locations depending on whether you have Windows XP or Windows Vista/Windows 7:
    • Windows Vista\Windows 7\Windows 10:
      C:\Users\(Your Windows Account Name)\AppData\Roaming\Microsoft\FSX
The dll.xml file is in this folder.  (Note that this is also the location of another very important file - your fsx.cfg)


Problem 1 - newline characters:

There are invisible formatting characters that make up what's called a "newline" in a text file.  In Windows and a couple of other operating systems the newline sequence is "CR LF" - those stand for "carriage return" and "line feed" - they're terms that originated a long time ago with telegrams and mechanical typewriters. In Unix or Linux based operating systems however, the standard is just a single LF character. This is what happens with certain installers by other companies, they're stripping the CR characters out of each newline the file and making it the Unix/Linux format with just LF. Windows Notepad can't read Unix style newline formating, so you'll see just a string of text with no line breaks when you open one of these corrupted files with it.
  1. Download a copy of Notepad++ here (which can read Unix/Linux text files) and you can actually see these characters and fix them:
  2. In the program, go to View/Show Symbols/Show End of Line.
  3. You'll now see a bunch of black and white boxed CR and LF characters at the end of each line in a good dll.xml file.   If you see just LFs, the file's been corrupted.
To fix the LFs, you can do one of two things:
  1. Go through manually, position the cursor before each LF and then press Ctrl+M, which inserts a Windows newline. (CR LF)
  2. The much easier method is to go to Edit/EoL Conversion and Select Windows Format.  If Windows is greyed out, select Unix Format first, and then move it back to Windows. It'll automatically convert all the LF to CR LF.
If that's the only thing that was wrong with the file, you're good to go and your addons should start working again because FSX can now read the file.

Problem 2 - truncated/orphaned pieces of entries:

Sometimes the file structure itself is corrupted and you'll see entries and lines out of order. For these, use the other entries as an example and attempt to place them in the proper format. If you are uncomfortable, or need additional help, you may
find some success in our customer forum located at forum.pmdg.com.

It is a very good idea to back up your dll.xml file before installing an addon, just to ensure that you have a good working copy to refer to in case the addon corrupts it.