The system requirements for 32-bit AutoCAD: 

• Intel® Pentium® 4 processor, 2.2 GHz Recommended
• Microsoft® Windows Vista™, Windows® XP Home and Professional (SP2), Windows® 2000 (SP4)
• 512 MB RAM
• 750 MB free disk space for installation
• 1024x768 VGA with True Color
• Microsoft® Internet Explorer® 6.0 (SP1 or higher)
• Available on CD (Worldwide) and DVD (select countries and languages)

Additional System Requirements for 64-bit AutoCAD

• Windows XP Professional x64 Edition and Windows Vista 64-bit
• AMD64 or Intel EM64T processor
• 1GB RAM, 2GB for Windows Vista 64-bit
• 750 MB free disk space for installation

AutoCAD 64-bit cannot be installed on a 32-bit Windows Operating System.

The System requirements for Windows Vista or 3D modeling (32 and 64-bit AutoCAD)

• Intel® 3.0 GHz or greater
• 2 GB RAM or greater
• 2 GB free hard disk available not including installation
• 1280 x 1024 32-bit color video display adapter (True Color) 128 MB or greater, OpenGL®, or Direct3D® capable workstation class graphics card. 
• For Windows Vista, a Direct3D capable workstation class graphics card with 128 MB or greater is required.