If you want to play the real game on a low-end PC, it is already quite well-optimized. Official requirements from Steam include: Revisiting Street Fighter IV's iOS Ports
If you are looking for a portable or lower-spec version of Street Fighter IV , these are the official alternatives: street-fighter-iv-game-on-pc-highly-compressed-gameboy
Super Street Fighter IV: 3D Edition is the only official Nintendo handheld version of the game. If you want to play the real game
The legitimate Street Fighter IV requires approximately 4.5 GB to 10 GB of hard drive space. street-fighter-iv-game-on-pc-highly-compressed-gameboy