Minimum:

Supported OS: Windows® XP/Vista (only)
Processor: 3 GHz Pentium 4 or AMD Athlon 3000 (3.5 GHz Pentium 4 or AMD Athlon 3500 recommended)
Memory: 1 GB of RAM
Graphics: 128 MB DirectX 9.0c-compliant, Shader 3.0-enabled video card (256 MB recommended) (see supported list*)
Sound: DirectX 9.0c-compliant sound card (NVIDIA nForce or other motherboards/soundcards containing the Dolby Digital Interactive Content Encoder required for Dolby Digital audio.)
DirectX: DirectX 9.0c
Hard Drive: 7 GB free
Peripherals supported: Windows-compliant keyboard and mouse, Xbox 360 Controller for Windows
Multiplayer: Broadband Internet connection with 128 kbps Kbps upstream or faster.
*Supported video cards: ATI RADEON X1600-1950 / HD 2000 / 3000 series, NVIDIA GeForce 6600-6800 / 7 / 8 series ; Laptop versions of these cards are not fully supported. These chipsets are the only ones that will run this game.

Tom Clancy's Rainbow Six Vegas 2 screenshots