This game is a port of the Games for Windows - Live version that was released in 2009. If you buy the Untold Stories Bundle here on Steam, it will be the same as upgrading to Resident Evil 5 Gold Edition.
Resident Evil 5 system requirements
Operating System: Windows 7
Processor: Intel Core 2 Quad 2.4GHz or better, AMD Phenom II x4 3.4GHZ or better
Graphics Card: 512 MB, NVIDIA GeForce 9800 series or better, ATI Radeon HD 7770 or better