I used to play a lot of San Andreas Multiplayer on my PC. It's actually fun to mess around with people on many different servers, especially those who get to much into the game and get pissed off by anyone who doesn't do what you should do in the server. You got all different servers; - Roleplay (RP) which is basically pretending to be the character you see on the screen. It's more fun than it sounds like. - Deathmatch (DM) which is self explanatory, just killing each other. - Stunt, which is riding around on bikes, cars and other vehicles and jumping over self build ramps. - Freeroam, which differs per server but in most of the servers it's DM combined with Stunting. It's quite a fun game and any PC can run it, let me know if you're planning on playing or if you got any questions. You can download the multiplayer version here; SA-MP San Andreas Multiplayer mod for Grand Theft Auto (GTA SA) you will need the regular version of San Andreas fully installed first. Ciao!
You can just download a pirated version and install the multiplayer mod on that one, it works perfectly!
I don't know that much about Steam to be honest. If you got San Andreas installed on your PC it has to work, as the multiplayer mod asks for the installation folder of the Singeplayer version.
Loved this fucking mod, so much fun honestly. I'd be willing to play somebody if they posted the server they will be on? Would love to drive around with some fellow blades...