Launching Sims 4 from external hard drive
EmmaBeeYT You will in fact have to "download" Sims 4 while using the laptop. The game data on the external drive isn't the only data that matters here—there are also registry entries and other hidden files that tell the App that Sims 4 is installed and you own it and have a right to play it. These files get created during the install process and are specific to the machine in question. They're also placed on the system drive (by default; there are ways to change this but they're not recommended) regardless of where you install the game itself.
Tell the App to install Sims 4 to the location where it's already installed, and the App may simply verify the data and finalize the install. Or it may download some content again. I've seen both happen when testing, sometimes in the same session.
