Polish site Polygamia offers system requirements for The Witcher 2, which they say they received from CD Projekt (thanks Destructoid). Interestingly, Google Translate says the English word for Wiedźmina is PlayStation. Here are the translated specs:

Recommended:

Processor: Intel Quad Core or equivalent AMD
Graphics Card: GeForce 260, 1GB memory / Radeon HD 4850 with 1GB memory
Memory: 3GB on Windows XP and 4GB for Windows Vista and Windows 7
Hard Disk: At least 16GB of free space
The requirements are low, but I think it could be expected. Finally, the game looks gorgeous, and as we know, the quality of the graphics need to go better components.

Minimum:

Processor: Intel Core 2 Duo 2.2 GHz or equivalent AMD
Video Card: Nvidia GeForce 8800 512 VR or similar ATI
Memory: 1 GB for Win XP / 2 GB for Win XP
Hard disk: 16GB