How do you get a patch off a comptur game

Most computer games cannot have patches removed without completely re-installing the product. For World of Warcraft, not only would you have to reinstall the game, you also cannot play unless your game has the latest patch installed.

If a game does allow a patch to be removed (like mods and user-generated content with Oblivion) there is usually an option in the game's launcher to enable or disable certain content or patches.