These are all the things you need to follow this guide.

Requirements

  • GTA: San Andreas 1.0 US (instructions for downgrading are included below)
  • Text editor (e.g., Notepad++)
  • Software capable of extracting compressed files (I personally recommend NanaZip)
  • Time and patience

Installing the Game

Do not download a pre-modded version of GTA. Use either the original 1.0 US installer or download it from Steam/Rockstar Games Launcher (RGL).
If you want to verify that your game files are intact, you can use GTA Healer.

Whether installing from the original DVD or via Steam/RGL, you must keep the installation folder outside the Program Files directory. Windows often blocks modifications there, which can cause errors.
If you installed the game via Steam on a different drive than your main Steam installation, it will usually be placed inside a Steam library folder (e.g., SteamLibrary), which is fine and safe for modding.

Downgrading

To install mods, the game must be downgraded to version 1.0 US.
I recommend following this guide by TJGM, which explains the differences between game versions in detail. Once the downgrade is complete, continue to the next section. If you can’t download the downgrader from MEGA for some reason, use this Mediafire link.

Redistributables

Many .asi mods require C++ Redistributables, which are usually installed automatically with software or games. If your PC is freshly formatted or has few programs installed, you may need to install them manually.

The same applies to DirectX End-User Web Installer, since Windows does not include older DirectX components. Installing it can fix graphical mods and issues with older games.

Recommended packages:

For a more detailed explanation, check this guide.