For reference (taken from a press release on this very topic)
PC MINIMUM System Requirements - OS = Windows XP SP3 / Windows Vista SP1 / Windows 7
- Processor = 1.8GHz Intel Core 2 Duo or equivalent AMD CPU
- Memory = 1 GB RAM for Windows XP / 2 GB RAM for Windows Vista and Windows 7
- Hard Drive = 15 GB
- DVD ROM = 1x Speed
- Sound Card = DirectX 9.0c compatible
- Direct X = DirectX 9.0c August 2008 (included)
- Input = Keyboard / Mouse
- Video Card = 256 MB (with Pixel Shader 3.0 support). Supported Chipsets: NVIDIA GeForce 6800 or greater; ATI Radeon X1600 Pro or greater. Please note that NVIDIA GeForce 7300, 8100, 8200, 8300, 8400, and 9300; ATI Radeon HD3200, and HD4350 are below minimum system requirements. Updates to your video and sound card drivers may be required. Intel and S3 video cards are not officially supported in Mass Effect 2.
PC RECOMMENDED System Requirements - Windows XP SP3 / Windows Vista SP1 / Windows 7
- 2.6+ GHz Cure 2 Duo Intel or equivalent AMD CPU
- 2 GB RAM
- ATI Radeon HD 2900 XT, NVIDIA GeForce 8800 GT, or better recommended
- 100% DirectX compatible sound card and drivers
- DirectX August 2008
NOTES: For the best results, make sure you have the latest drivers for your video and audio cards. Laptop or mobile versions of the above supported video cards have not had extensive testing and may have driver or other performance issues. As such, they are not officially supported in Mass Effect 2. Intel and S3 video cards are not officially supported in Mass Effect 2.