This process will work for Windows 7 and Vista (some details might vary for other Windows versions). It has worked flawlessly for me (including the intro and in-game videos) under Windows 7 Pro x64 SP1 on an Intel-based system with NVIDIA graphics (non-SLI). I cannot vouch for other configurations:

1. From Steam, install Jagged Alliance 2 Gold; run the game once to assure the complete installation of all modules.

2. Create a folder named "Games" (or "Modded Games", or whatever you want to call it, without the quotes) in the C:\ folder. This is done to avoid potential conflicts with UAC (User Account Control) permissions inherited from the stock Windows "Program Files" or "Program Files (x86)" folder that may occur if you generally log in to Windows using a 'Standard User' account rather than an 'Administrator' account. (OBSOLETE -- YOU CAN NO LONGER PREVENT STEAM FROM AUTOMATICALLY UPDATING YOUR STEAM COPY OF ANY GAME! Follow all steps as directed, but see note in step 6 if you wish to access the modded game from within your Steam Library: If you wish to apply the patch directly to the game folder under Steam, you're welcome to try, but subtle game glitches are a possibity; if you do, I recommend you disable "Automatically keep this game up to date" in its Properties to avoid unwelcome surprises should Steam actually do so, and also avoid verifying the game's cache to prevent Steam from overwriting your newly patched game files).

3. COPY the folder "Jagged Alliance 2 Gold" from your C:\Program Files [or Program Files (x86)]\Steam\steamapps\common folder to your newly created C:\Games folder. If disk space is at a premium you can 'Delete Local Content...' for Jagged Alliance 2 Gold in your Steam Library from the game's right-click menu once you've verified that this patch has worked for you and you don't have (or care about) saved games that would require the standard Steam JA2 Gold v1.12 install. Note, however, that future, major, v1.13 Patch releases will likely work best on a clean, unmodified copy of the game.

4. Run the downloaded Unofficial v1.13 Patch (JA2v1.13 Build 7435, 28 August 2014)
ja2v1.13-7435en[area.xrmb2.net], directing it to unpack in your "C:\Games\Jagged Alliance 2 Gold" folder, overwriting any existing files.

5. Run the downloaded Update Version for Release 7435: Build: 7609, 25 October 2014[web.archive.org], directing it to unpack in your "C:\Games\Jagged Alliance 2 Gold" folder, overwriting any existing files.

6. Create a shortcut by right-clicking on the "INI Editor.exe" file in the "C:\Games\Jagged Alliance 2 Gold" folder and selecting "Create shortcut"; Rename the created shortcut to "Jagged Alliance 2 Gold" or "Jagged Alliance 2 Gold 1.13", or whatever you like, and move it to your desktop or Start Menu. Alternatively: If you really want to access the patched game from your Steam Library, you can safely add it by using the Steam Client's 'Games>Add a Non-Steam Game to My Library...' drop-down menu, and you won't have to worry about Steam inadvertantly "auto-updating" your modded game.

7. Double-clicking your new shortcut should allow you to run the v1.13 game. (Display resolutions, along with many other game options, are selected by running 'INI Editor.exe' in the "C:\Games\Jagged Alliance 2 Gold" folder. It serves as the game launcher in addition to an .INI file editor.)

Note that this ONLY applies to Jagged Alliance 2 Gold from Steam (or elsewhere). It does NOT work with Jagged Alliance 2: Unfinished Business or Jagged Alliance 2: Wildfire. Also, remember that this is an unofficial patch and various bugs still exist. Any other necessary tweaks I'll leave for others to supply. As of this writing the latest "STABLE" version is the now Current official Update Version for Release 7435: Build: 7609, 25 October 2014, linked in step 5 above.) Further information and documentation including other language versions can be found at JA2 v1.13[ja2v113.pbworks.com]. If you're interested in the latest v1.13 (UNSTABLE) builds, builds for Jagged Alliance 2: Unfinished Business, or any other v1.13 projects in the works, you can find them at v1.13 Modders (Development Discussions)[thepit.ja-galaxy-forum.com].

For a solution to the lag problem under Windows 10, see the comment below by bscoms posted on Jun 1, 2016.

Good luck.


(Last edited Oct. 31, 2020: Download Links updated. Thank you @XDms for the heads-up!)