Minimum:  CPU 2.4+GHZ Intel or 2.0+GHZ AMD, 1GB RAM (XP) / 2GB RAM (Vista), NVIDIA GeForce 6 series(6800GT or better) / ATI 1300XT or better (X1550, X1600 Pro and HD2400 are below minimum system requirements), DirectX 9.0c compatible sound card and drivers, 12GB free HDD space, Windows XP or Vista
 
Recommended: CPU 2.6+GHZ Intel or 2.4+GHZ AMD, 2GB RAM, NVIDIA GeForce 7900 GTX or higher / ATI X1800 XL series or higher, DirectX 9.0c compatible sound card and drivers - 5.1 sound card recommended, 12GB free HDD space, Windows XP or Vista

The Mass Effect Config program will automatically adjust your settings on first run, to attempt to give you an optimal play experience. As with all PC games, computer performance varies from system to system and adjustments can be made via the Config or through the in-game options to tailor your experience.