Pete,
I've just purchased and registered a copy of FSUIPC4 for FSX and had a little trouble with the installation, in that the "Add Ons" option in the menu bar didn't appear, and I had to run the installation program twice to get this to show and to insert the registration key. On re-starting FSX a couple of times after that, all was well, with the FSUIPC option available under Add Ons.
When starting FSX up again today, the "Add Ons" option has disappeared again.
The Modules directory is still in the FSX root folder, and I note your reference to the file DLL.XML in the user guide, however I haven't accessed this or done anything to change it's location.
I have however downloaded, and am trying out a copy of FS Commander, which may have caused the problem.
Could you kindly advise.
Thanks.