The Aliens: Colonial Marines Facebook Page notes that AvPGalaxy has word that Steam will begin offering preorders of Aliens: Colonial Marines today, also providing system specifications for Gearbox Software's upcoming shooter. Here's word:

Minimum Specs: Operating System: Windows XP SP3. Processor: 2 GHz Intel Dual Core Processor. RAM: 2GB RAM (XP),2GB RAM (Vista). HD: 20GB free hard disk space. Optical Drive: DVD. Sound Card: DirectX 9.0c compatible. Video Card:NVIDIA GeForce 8500/ATI Radeon HD 2600 (256 minimum).

Recommended Specs: Operating System: Windows XP SP3/Vista/Windows 7. Processor: 2.3 GHz Intel Quad CoreProcessor. RAM: 2GB RAM. HD: 20GB free hard disk space. Optical Drive: DVD. Sound Card: DirectX 9.0c compatible. VideoCard: NVIDIA GeForce GTX560/ATI Radeon HD 5850 (512 minimum).

Other Requirements: Initial installation requires one-time internet connection for Steam authentication; software installations required (included with the game) include Steam Client, DirectX 9, Microsoft .NET 4 Framework, Visual C++ Redistributable 2005, Visual C++ Redistributable 2008, Visual C++ Redistributable 2010, and AMD CPU Drivers (XP Only/AMD Only).