Here are the Bioshock Infinite System Requirements (Minimum)
CPU: Intel Core 2 DUO 2.4 GHz / AMD Athlon X2 2.7 GHz
CPU SPEED: Info
RAM: 2 GB
VIDEO CARD: DirectX10 Compatible ATI Radeon HD 3870 / NVIDIA 8800 GT / Intel HD 3000 Integrated Graphics
DEDICATED VIDEO RAM: 512 MB
PIXEL SHADER: 4.0
VERTEX SHADER: 4.0
OS: Windows Vista Service Pack 2 32-bit
FREE DISK SPACE: 20 GB
SOUND CARD: Yes

Bioshock Infinite Recommended Requirements
CPU: Quad Core Processor
CPU SPEED: Info
RAM: 4 GB
VIDEO CARD: DirectX11 Compatible, AMD Radeon HD 6950 / NVIDIA GeForce GTX 560
DEDICATED VIDEO RAM: 1024 MB
PIXEL SHADER: 5.0
VERTEX SHADER: 5.0
OS: Windows 7 Service Pack 1 64-bit
FREE DISK SPACE: 30 GB
SOUND CARD: Yes