Note that GGPO was attacked by DDOS since FightCade was launched and has since been taken down indefinitely.Edit
How to Play 3S on GGPO Edit
Notice: GGPO has now been indefinitely taken down. Go to Play 3S on FightCade.
1. Download and install GGPO. Create an account on their forum
2. Unzip this file and put the files in the 'savestates' folder in GGPO
4. If these folders don't exist. Open GGPO once for them to be automatically created
5. Join the "Street Fighter Tres" room. Set your buttons after the match starts
Ready-to-Play Package Edit
Ready-to-Play Package by RVN: http://www30.zippyshare.com/v/17652368/file.html
Simply un--rar the package and play . Obviously you will need a GGPO account, and to deal with opening ports.
Note: It is illegal to download and keep ROMs for over 24 hours unless you own the actual game.