Another couple of tips:
Install Orbiter into a root directory (e.g. into C:\Orbiter). If you put it in Program Files, My Documents, etc, then you may have a struggle with default rights. (Not saying you can't do it ... but just make your life easy and put it in a root).
When you install the core distribution, the D3D9 or addons from orbithangar.com (or other download repositories), save the original download files in a download directory - e.g. C:\OrbDL. This saves you from having to re-download things when you want to make a clean install. (E.g. it's typical to have different clean installs for specific projects, or simply when you want to get clean again after maybe putting on something that is not working properly ... such as a very old add on).
Typically you just extract all and unzip an install over the top of your Orbiter directory. However, sometimes the directory structure is incorrect in the download (e.g. a extra root directory), or it's an exe installer file inside the zip. For these, you need to extract them and then move across the right subdirectories, or you need to extract and run the installer.
For D3D9, when you first install and select it as your graphics client in Orbiter_NG.exe, go into Advanced setup and click 'Create Symbolic Links'. This fixes up some links behind the scenes that are needed for things to work.
Keep going ... once you get past these teething issues, you are in for a treat.
