Owners of the PC retail version of Super Street Fighter 4 can transfer their game, but not their DLC, to the Steam version.
Games for Windows Live will reportedly shut down in July, taking the online versions of its games permanently offline. A post on Capcom Unity lays out how GFWL owners can receive free access to the Steam version.
Players who bought the game on Steam will simply receive a new Steamworks-enabled version of the game starting on May 30, with the option to transfer over the old version's latest save file. Players who bought the game through GFWL's store or retail can use the same CD key to unlock a copy on Steam.
However, any DLC content purchased through GFWL will not be transferred over, and players will have to purchase it again on Steam if they want continued access. The Games for Windows Live version won't be deleted, but it will lose online connectivity when the service shuts down.
Super Street Fighter IV PC owners will be able to upgrade to Ultra Street Fighter IV starting on August 8, two months after the upgrades hit consoles.