Installation of the mod is peculiar in that it must be installed in the plugins folder found inside the folder where SC4 is installed. In addition, these mods are HD Textures.

Before installing this mod make sure that SC4 works with Hardware Rendering (DirectX Rendering)

Installation: This download doesn't contain an Installer. Unzip the mod and save the content somewhere, each sky background will have it's own folder.
To install the sky texture open the "Maxis" Plugins folder (C:Program FilesMaxisSimcity 4Plugins, the path will be different if you have the game installed in another place), you will see 5 PNG files: Background3D0, Background3D1, Background3D2, Background3D3, Background3D4. These are Maxis backgrounds for every zoom. Remove them and save in another place outside of the Plugins folder (maybe you will want to use them again). Then choose the sky texture, open its folder and copy files to Plugins.
PNG files should be located in the root plugin folder, don't move the whole sky background folder there!
Installing backgrounds in the second Plugins folder (in My Documents) doesn't work too.

You can install only one of the versions from this mod and it should be installed in the Plugins folder found in the SC4 installation folder. Be sure to read the instructions before installing this mod

Un-Installing: To un-install the files, simply delete the files from the plugins folder. Then you should replace them by another custom sky background or by Maxis default files.
Tip: If you will remove all background files from Plugins, the game will still work, but you will get completely black sky background. Some players can find it useful.

The following paths are used by the installer system. If you have your game installed in another place, you should change the path for Dat files.