The y2k3environment.exe file you have requested: Add Ons / Others / Y2K3 Environment and Extra Pack - 3.32mb is not available. Perhaps try browsing all files for the game ARMA: Cold War Assault and upload any files you want to share or are missing. This is the only information we could locate:
To install, extract the archive to your Operation Flashpoint directory. Then go to the Y2K3 directory, and run the install.bat file. If the install goes well, you should be able to use the hisky directory like a regular mod folder. (ie. add -mod=Y2 Pappy Boyington, creator of the Y2K3 mod has released this "Environment pack and more" to further enhance your Y2K3 or OFP experience. The pack contains a new sky which is several sky mods combined to give you the best effect.