File Description:
Temporary file created for games downloaded by Valve's Steam game distribution service; named by a game filename, an identifier, and the ".steamstart" suffix (e.g., game.exe.1234.steamstart); sometimes created when games do not load properly.

STEAMSTART Related File Extensions: .SRM, .SPRITE, .SP2, .SOUNDS, .SNDA, .SMZIP, .SMC, .SM,