Windows 7 System Requirements

If you want to run Windows 7 on your PC, here's what it takes:

1 gigahertz (GHz) or faster 32-bit (x86) or 64-bit (x64) processor

1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit)

16 GB available hard disk space (32-bit) or 20 GB (64-bit)

DirectX 9 graphics device with WDDM 1.0 or higher driver

Additional requirements to use certain features:

Internet access (fees may apply)

Depending on resolution, video playback may require additional memory and advanced graphics hardware

Some games and programs might require a graphics card compatible with DirectX 10 or higher for optimal performance

For some Windows Media Center functionality a TV tuner and additional hardware may be required

Windows Touch and Tablet PCs require specific hardware

HomeGroup requires a network and PCs running Windows 7

DVD/CD authoring requires a compatible optical drive

BitLocker requires Trusted Platform Module (TPM) 1.2

BitLocker To Go requires a USB flash drive

Windows XP Mode requires an additional 1 GB of RAM, an additional 15 GB of available hard disk space, and a processor capable of hardware virtualization with Intel VT or AMD-V turned on

Music and sound require audio output

Product functionality and graphics may vary based on your system configuration. Some features may require advanced or additional hardware.

Source: http://windows.microsoft.com/systemrequirements