Steam is fine, but very slooooow loading, more in a old low range PC. GOG is somewhat faster, apart you can download the game, which normally is launched with the GOG client, but you can search the executable and launch the game directly, without GOG. Another fine site for free games is DigiPen, it’s a tech academy which exposed hundred of games of any kind, work of the students, which you can download, but there are also games which won’t work in a very old PC, ther you must test it. It’s listed by years, look in the older ones. Look also in the list of OpenSource games, , well, if Mineseeker works in your Lap, most of these also will do it.