The game you picked isn't a valid installation of Grand Theft Auto: San Andreas

As shown in the title of this topic, I try to pick a GTA:SA directory but it gives me an error with that exact message. Is it because I’m doing it wrong by not picking the directory that’s a sub folder of the “Rockstar Games” folder? (I have multiple directories of the game for testing other mods aswell as a backup one, so that’s why I’m asking. I also didn’t install it through Steam so that may also be the reason as to why it doesn’t work)
Here’s a screenshot of the error message aswell as the directory I’m trying to pick:

Is this a cracked copy?

Choose the base game folder

Yeah, I lost the install CD but I do have the original on my older computer. I’ll try and see if it works there.