Voila il dise ca
" * Before downloading any of the extension packages, download and install the base package, and make sure it works correctly.
* To install a hi-res package, simply download to your main Orbiter directory and unzip. The files should end up in the Textures2 subdirectory.
* You don´t need to download multiple resolution packages for a single planet. The higher-res packages already include all lower-res versions. The exception is Mars, where the L8 package must be installed in addition to any higher-res packages.
* If you install the Planets & Moons package, you don´t need to install any of the packages marked with ´*´.
* Installing the high-resolution packages can affect the simulation frame rates and loading times. They should be used with caution, in particular on low-end computers. "