You can upgrade to Windows Vista from an earlier version of Microsoft Windows or you can perform a "clean installation" of Windows Vista. When you perform a clean installation, files that were part of the previous installation are deleted before you install Windows Vista. This article also provides tools to help you determine which kind of installation is right for your computer.
Requirements

Internet Connection

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System requirements

Windows Vista Home Basic

• 800-megahertz (MHz) 32-bit (x86) processor or 800-MHz 64-bit (x64) processor
• 512 megabytes (MB) of system memory
  
  Note: On system configurations that use system memory as graphics memory, at least 448 MB of system memory must be available to the operating system after some memory is allocated for graphics.
• DirectX 9-class graphics card
• 32 MB of graphics memory
• 20-gigabyte (GB) hard disk that has 15 GB of free hard disk space
• Internal or external DVD drive
• Internet access capability
• Audio output capability

• 1-gigahertz (GHz) 32-bit (x86) processor or 1-GHz 64-bit (x64) processor
• 1 GB of system memory
• Windows Aero-capable graphics card
  
  Note This includes a DirectX 9-class graphics card that supports the following:
  • A WDDM driver
  • Pixel Shader 2.0 in hardware
  • 32 bits per pixel
• 128 MB of graphics memory (minimum)
• 40-GB hard disk that has 15 GB of free hard disk space (the 15GB of free space provides room for temporary file storage during the install or upgrade.)
• Internal or external DVD drive
• Internet access capability
• Audio output capability