I may have mentioned this before but here are the latest official Recommended System Requirements from the Autodesk website:
The following system requirements are recommended for effective use of Autodesk Civil 3D 2007 software.
Autodesk Civil 3D 2007 recommended configuration (excluding server components that are used with project management capabilities):
Intel® Pentium® IV processor, 3 GHz or higher
Microsoft® Windows® XP Professional or Home Edition (SP2), Windows XP Tablet PC Edition (SP2), or Windows 2000 (SP4)
2 GB RAM
5 GB free disk space for installation
1280x1024 with true color, OpenGL®-capable workstation class graphics card or DirectX® 9 support
Mouse, trackball, or compatible pointing device
Microsoft Internet Explorer 6.0 (SP1 or later)
Click on the title of this post to see the Autodesk page.