You can find installation and launching instructions as well as download mirrors in a discussion thread on our forum
Also download this patch for Mega Build that fixes some problems and adds more content.

Half-Life 2 Beta: Mega Build is a compilation of all fixes, patches and mods made for the Half-Life 2 "beta" since 2003.
No more searching, no more conflicting content, and no longer will you have to have several installations of the beta with different patches.

This build contains:
-Mod Launcher - an app for launching mods or packs for Mega Build
-LeakNet HL2 Beta:Launch the game without any mods, running only content from the HL2 folder.
-E3 2002 :The cancelled E3 2002 presentation made by Valve, also includes in-development early versions of various demos.
-E3 2003:The E3 2003 presentation shown publically by Valve, also includes in-development early versions of various demos.
-2000 Mappack:Maps created by Valve from Late 2000.
-2001 Mappack:Maps created by Valve from January 2001 to Mid 2001.
-2001-2002 Mappack:Maps created by Valve from Late 2001 to Early 2002.
-2002 Mappack:Maps created by Valve from Early-ish 2002 to Mid 2002.
-2002-2003 Mappack:Maps created by Valve from Late 2002 to Early 2003.
-2003 Mappack:Maps created by Valve from Early-ish 2003 to Mid 2003.
-2003 Leak Story:Maps present in the original leaked build of Half-Life 2 from September 2003(fixed by XJR9000).

Every map from these mods has been fixed up and made playable, all with era-appropriate visuals depicting how the game looked at various stages of development.

Attention! Do not expect a fully playable game from this build. It's not an "Old storyline resoration", "beta mod", or anything like that.
The maps contained in this pack should be launched from the developer console, using the "map" command.
The separate game folders should be launched with the LeakNet Mod Launcher (ModLauncher.exe)

You should also expect frequent game crashes. Unfortunately, the beta's engine, even patched with LeakNet, is very unstable.
Here are some of the common causes of a crash:
-Attempting to change level after being grappled by a barnacle
-Saving your game on a level containing a 'phys_' entity.

Alternative Google Drive link