Windows 10 OS
On Windows 10 you just need to mount the ISO or use the original FL CD and run all executables and game files with Windows XP SP2 support. (Right click exe files -> compatibility menu).
When Freelancer is started for the first time it may install/activate DirectPlay - this is technically needed to play Freelancer. It won't take long to do those small changes in the windows settings.
How to install?
1. open the ISO
2. start the setup/install/autorun executable
3. follow the install instructions and install the basic freelancer game
4. it is recommended to choose "full installation"
5. When you would like to mod / update your installation you can use freelancer mod manager (freeware) or drop mod folders manually into your game folders to update your versions. It is recommend to make a copy of the original game folder with an edited name in order not to troubleshoot or crash your working installation later. When you make a backup keep in mind that Freelancer uses two folders to store your game files. First is the common game folder that users are used. The second is in the user's data folders under "... \MY GAMES\Freelancer" - it is recommend to backup those folders, too when you make changes to the original Singleplayer version. When you would like to play the other you can start the FL.exe from specific unmodded backup folder - this way you just need to replace the "MY GAMES\Freelancer\..." user's folder, when you switch back to single-player and campaign story mode. Other mods are overwriting this user folder with your server multiplayer IDs. You should keep an eye on them, don`t share them to others - when other people know your ID they can do changes on your accounts. When you loose the files you maybe in danger of loosing entrance to your existent multi-player chars. I will release more information about freelancer multiplayer IDs later on another place of this board.
When you just want to play the Original Freelancer start the setup from the ISO/CD now and if you like enhance it with smaller or bigger mods you wanna play (Widescreen Mod Download is above - introduces higher resolutions and resolution auto detect / screen resize).
The game can be installed on other OS, too. From Win9x up to WinXP/Vista up to Win7,8,8.1 there are more or less easy instructions how to install it all over the web. When you have found a certain solution or having serious issues your free to communicate here. There are even people who managed to install and play it on MAC & Linux OS systems!