Good News!!! If you are running Microsoft Windows Vista on your PC already, you do not have to pay heavily for a hardware upgrade if you intend to install Microsoft Windows 7.

Below is the comparision of Minimum system requirement for Windows Vista & Windows 7:

Windows 7:

• 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

Windows Vista – Home Premium / Business / Ultimate:

• 1 GHz 32-bit (x86) or 64-bit (x64) processor
• 1 GB of system memory
• 40 GB hard drive with at least 15 GB of available space
• Support for DirectX 9 graphics with:
  • WDDM Driver
  • 128 MB of graphics memory (minimum)
  • Pixel Shader 2.0 in hardware
  • 32 bits per pixel

Additional requirements to use certain features:

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

Windows Touch and Tablet PCs require specific hardware

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.

For more information, visit following links:

http://www.microsoft.com/windows/windows-7/get/system-requirements.aspx

http://news.softpedia.com/news/Windows-7-System-Requirements-110635.shtml