Windows 8 does not need a powerful computer to run. Any computer that is currently running Windows 7 or Windows Vista has the ability of running Windows 8.
Below are bare minimum requirements for Windows 8 but should probably have lot more than the bare minimum.
• 1GHz or more that supports PAE, NX, and SSE2
• 16GB hard drive minimum for the 32-bit or 20gb for the 64-bit operating system
• 1GB of RAM for the 32-bit or 2GB for the 64-bit
• Graphic Card that supports DirectX 9 with WDDM (Windows Device Model Driver) Driver in minimum
• Screen resolution of 1366 by 768