According Mary Jo Foley’s All About Microsoft blog, Microsoft made the final system requirements for Windows 7 available today. Here it is:
- 1 GHz processor (32- or 64-bit)
- 1 GB of RAM (32-bit); 2 GB of RAM (64-bit)
- 16 GB of available disk space (32-bit); 20 GB of available disk space (64-bit)
- DirectX 9 graphics device with WDDM 1.0 or higher driver
You can learn more here
The requirements look reasonable and realistic this time around compared to Vista which recommended 512 MBs of RAM as the minimum. If you plan on storing a lot of data on your PC, I suggest you choose more than 16 or 20 GBs to install it on.