Since ubi.com client is down and they no longer support this game longer due to lack of players.

First:
1. Install Ghost Recon.
2. Install Ghost Recon Desert Siege.
3. Install Ghost Recon Island Thunder.
4. Patch to 1.3 located in GRecon.iso in "nocd1.4 crack..." folder. (you have to patch 1.3 before you patch up to 1.4!)
5. Patch to 1.4
6. Unrar GhostRecon.exe from GHOST.RECON.14.ENG.NOCD.ZIP
7. Replace the original GhostRecon.exe with the unzipped GhostRecon.exe to the installation path.

Now you have the game successfully installed, now how to get multiplayer to work.
1. Install Tunngle from http://www.tunngle.net and register an account.
Watch this video - http://www.youtube.com/watch?v=W5Ymp35Q1kU
2. Instead of writing "call of duty" at 7:52, write "ghost recon" instead and push Enter.
Join "Tom Clancy's Ghost Recon" lobby.
3. When you have join the lobby, start Ghost Recon and press on "Multiplayer" and let it be on LAN, it will pop up servers there if there is any players which have start any.
To list your server there you must have 2348 UDP port forwarded.
http://www.portforward.com will help you how to port forward.