How to get work Half-Life under Xash3D:
step-by-step instruction for anyone.
It is important to understand, that Xash3D is an independent game engine. It's not a mod for Half-Life, so to get work Half-Life under it, you have to make a separate installation of the game. Please follow these steps carefully and you won't confuse with anything.
1. Please install a Half-Life game properly at first. Currently, a full version of Half-Life can be purchased and activated via Steam. If you have a CD with an old WON version of Half-Life, you can use it too. But please remember, that it's recommended to update your WON version of the game with a patch 126.96.36.199 to be prepared for running latest Half-Life mods also, not only Half-Life itself. If you are not sure about which the version of the WON game you have installed, just run the game and look at the right lower corner of the game menu screen. There are some numbers with your game version. If it's not a "v46/188.8.131.52", please update your game. But you don't need to update your Steam version of the game with this patch. Use Steam update feature instead. Anyways, any Steam version of the game should be compatible and ready for running latest mods under Xash3D.
2. Download the latest version of Xash3D Engine. Currently, it's a build 2867 (v0.96). You can get it at the "Downloads" section. After downloading you will get a Xash3D_build2867_with_extras.zip file on your computer.
3. Now you have to create a separate folder for Xash3D installation. You can create this folder anywhere you want, but please don't create it inside that directory where your Half-Life is installed already (don't be a noob, LOL). It's better to use simple path to this folder and give it an appropriate name, something like "D:\Games\Xash3D". This folder will be your main Xash3D game directory.
4. Locate and open a folder with a basic Half-Life game content. For the WON version of game it can be something like "C:\Sierra\Half-Life\". You will see a "valve" directory inside. For the current Steam version of the game it can be something like "C:\Program Files\Steam\SteamApps\common\Half-Life". You also will be able to find a "valve" directory inside it. For the old Steam version of the game it can be something like "C:\Program Files\Steam\SteamApps\" folder. It's not a game folder in fact, but it's a folder with a main game's archive - half-life.gcf, which is containing a "valve" directory inside. Unpacked "valve" directory with all of its content is essential for installing Half-Life under Xash3D, so you need to download and install any appropriate utility, which can help you to open half-life.gcf and to extract its' content. You can use a GCFScape program for this operation, for example (you can also check a sample on how to open GCF-files and extract their content here).
5. Copy the whole "valve" folder with all of its' content from your Half-Life game folder (for WON or current Steam version of the game) or extract it from your half-life.gcf (for the old Steam version of the game) directly into the main Xash3D game directory (which was created at Step 3). So after that you get something like "D:\Games\Xash3D\valve" with a basic game content. If you are using any Steam version of the game as a source, after copying (extracting) of "valve" folder also check inside "valve\sound\common" folder. There are some launch_*.wav files. Copy them to the "valve\media" folder (these sounds are required for Xash3D game menu, but they present in this folder only in WON versions of the game).
6. Proceed to extracting a content of the Xash3D_build2867_with_extras.zip archive into the main Xash3D game directory. At first, you will get 2 more archives: xash_build2867.7z and xash_extras.7z. 7z files are 7-Zip archives, which can be extracted with 7-Zip program or with any other appropriate archiver. Continue their extracting into the Xash3D directory with overwriting of any existing files (some files in the "valve" folder have to be replaced). Finally, you will get the Xash3D directory with "docs", "source code" and "valve" folders inside, plus files #hl.exe, hl.exe, Install Notes.txt, menu.dll, readme.txt, vgui.dll and xash.dll.
7. Now you almost ready to run the game. But firstly, create a shortcut for hl.exe (located in the Xash3D directory) and put it onto your desktop (or into the Programs menu, for example). If you want to enable a console in the game, you have to edit a properties of the shortcut (right-click the shortcut and select a "Properties" tab in pop-up menu). Check the "Target" field and add there parameter " -console" (with space, but without quotes) after hl.exe. Click "OK". There is also #hl.exe in Xash3D directory, which can be used to start a dedicated server for multiplayer game (if you are interested in this feature).
8. Start your game via the created shortcut. At the first time, game runs in a windowed mode and 800x600 resolution. After an appearing of the game menu you will be able to edit your game preferences (fullscreen mode, other video resolution, sound effects, controls etc.) via "Configuration" menu. Please note, that in the "Sound" menu there is a "Disable DSP effects" checkbox. It is checked by default (since the build 2015). It's because DSP is an experimental feature in Xash3D. It adds environment effects to the sound, but can cause some wrong sound effects in different situations. So enable it "on your own risk". If you have some HD-textures for maps, decals or models (previously placed in "valve\materials" folder), you also need to enable "Allow materials" checkbox in the "Video options" dialog screen to make the game use them.
9. If you want to play any Half-Life or Xash3D mod, you have to install it or extract its' content into a separate folder inside a main Xash3D directory (same as for the standard Half-Life game). Follow an instruction that is appended to a mod, but make sure that any mod (with all of its' content) was placed into an individual folder. Any properly installed mod can be selected and activated via "Custom game" menu. You can also create a custom shortcut to run any mod. Just create a copy of the shortcut for hl.exe and add in the "Target" field parameter " -game FOLDERNAME" (with space, but without quotes) after hl.exe. "FOLDERNAME" here it's a name of the folder where your mod is located. For example, to run Opposing Force (when installed) you have to add " -game gearbox" parameter after hl.exe. In fact, it's an all the same system, which you can use to run any mod under standard Half-Life.
10. Make sure you have read an additional information about Xash3D posibilities and features (which is containing in documents in the "docs" folder, plus in those text files in the main Xash3D directory). Some information is also avaliable here, at ModDB. Please read the details, before you ask about something, that you don't know yet.