Not much in terms of the hardware needs of http://www.autodesk.com/autocad - AutoCAD 2011 has changed over the past few releases other than supported Operating Systems.

For 32-bit

• Microsoft® Windows® 7 Enterprise, Ultimate, Professional, or Home Premium, Microsoft® Windows Vista® Enterprise, Business, Ultimate or Home Premium (SP1 or later) or Microsoft® Windows® XP Professional or Home edition (SP2 or later)
• For Windows Vista or Windows 7: Intel® Pentium® 4 or AMD Athlon® dual-core processor, 3.0 GHz or higher with SSE2 technology; for Windows XP: Intel Pentium 4 or AMD Athlon dual-core processor, 1.6 GHz or higher with SSE2 technology
• 2 GB RAM
• 1.8 GB free disk space for installation
• 1,024 x 768 display resolution with true color
• Microsoft® Internet Explorer® 7.0 or later
• Install from download or DVD

For 64-bit

• Microsoft Windows 7 Enterprise, Ultimate, Professional, or Home Premium, Microsoft Windows Vista Enterprise, Business, or Ultimate (SP1 or later), or Microsoft Windows XP Professional (SP2 or later)
• AMD Athlon 64 with SSE2 technology, AMD Opteron® processor with SSE2 technology, Intel® Xeon® processor with Intel EM64T support and SSE2 technology, or Intel Pentium 4 with Intel EM64T support and SSE2 technology
• 2 GB RAM
• 2 GB free space for installation
• 1,024 x 768 display resolution with true color
• Internet Explorer 7.0 or later 
• Install from download or DVD

Additional requirements for 3D modeling for both 32 & 64-bit system

• Intel Pentium 4 processor or AMD Athlon, 3 GHz or greater; or Intel or AMD dual-core processor, 2 GHz or greater
• 2 GB RAM or more
• 2 GB hard disk space available in addition to free space required for installation
• 1,280 x 1,024 true color video display adapter 128 MB or greater, Pixel Shader 3.0 or greater, Microsoft® Direct3D®-capable workstation-class graphics card

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