Hardware:
Pentium, Celeron, or higher processor.
200 MB disk space.
512 MB RAM. 1 GB or more is recommended.
OpenGL graphic card recommended.
IntelliMouse recommended.
3-D digitizer optional.
3-D printer optional.
Operating systems:
Rhino 4.0 runs only on Windows 2000, XP Pro, XP Home, and Vista* including an Intel Mac with BootCamp or Parallels.
*Vista requires Rhino 4.0 Service Release 1 or above.
Rhino 4.0 will not run on Windows NT, 95, 98, or ME.
Native Windows x64 is not supported and will not be until the required development tools and libraries are available. There will be a free service release available as soon as possible after 4.0 ships. Rhino 4.0 does run as a 32-bit application on Windows x64.
Rhino 4.0 does not run natively on Mac OS X, but it is under development. Details...
Rhino 4.0 does not run natively on Linux, or any other operating system not listed above.

New Features:
Angle input added: Angle formats for rotate-related commands (Rotate, Rotate3D, ArrayPolar, RotateEdge, etc.) now can accept decimal degrees; degrees, minutes, seconds, gradians, and radians.
ToolbarLock: New command. Locks docked toolbars into place.
Enhanced Features:
Layout: PageLayout is now a built-in alias for the Layout command
Purge: Now deletes bitmaps saved as Wallpaper.
Sweep2: The rebuild curves option now allows the number of control points to be reduced to 2.
Bug Fixes:
3DFace: now supports ortho from the previous point, and it is now possible to snap to all previous points with the Point osnap
Alt+Drag did not properly copy selected control points. This is fixed.
BlendCrv: Input curves were sometimes not properly deleted. This is fixed.
BlendCrv: When using Trim=Yes and Join=Yes, the input curves are left behind. Result is that you have the two curves joined with the blend and the original two curves left. This is fixed.
Booleans: Several failure bugs fixed.
Crash bugs fixed: Dozens of crashes have been fixed throughout Rhino: Display, Meshing, Pullback curves to surfaces, Toolbars, Object Sorting, File I/O, STEP, Cancelling of time-consuming tasks, Drag & Drop Files, NetworkSrf, Curve-Surface intersection, Worksessions, Hatch UI, ArrayOnSrf, Dialog Localization.
Dimensions: Dimensions inside blocks did not display correctly when the view was rotated. This is fixed.
Dual monitor: Resizing the main Rhino window so it stretched across two monitors then closed and re-opened Rhino, the main window was incorrectly sized to fit the main monitor or the monitor that contains most of the window rectangle.
Now Rhino will let the window span multiple monitors and will only move or resize the window if one or more edges is off all the monitors.
Edit Toolbar button dialog box now supports Ctrl+A to select all of the text in an edit box.
Fair: The command did not stick closely enough to the tolerance. This has been improved.
FilletCorners: A failure bug has been fixed.
FilletEdge: Failed in some instances using a bad surface as input.
FilletEdge: Handles placed at surface seams could be incorrectly oriented. This is fixed.
HideInDetail: Objects hidden with the HideInDetail command incorrectly responded to object snaps in active views. This is fixed.
Intersect: Failed on some closed polysurfaces. This is fixed.
Intersect: Several failure bugs have been fixed.
Layer: Dragging layers with parents and children did not work correctly. This is fixed.
MergeFace did not use the default angle tolerance. This is fixed.
Mesh: One problem with slow meshing has been fixed.
OffsetNormal: A curve resulting from offsetting the edge of a sphere incorrectly contained a kink at the equator. This is fixed.
Open:DWG/DXF: Inserting or Importing dwg or dxf files incorrectly set the linetype scale in rhino to whatever it is in the AutoCAD file. This is fixed.
Open:DWG/DXF: Now only lightweight polylines with straight segments are read as polycurves.
Open: A crash opening earlier Rhino files with GHS data has been fixed with the HOT FIX release.
Osnap:Int: When zoomed out, too many objects could be in the pickbox causing a slowdown. This is fixed.
Pipe: When the Thick and Global options were used, the command incorrectly did not make the pipe correctly. This is fixed.
Properties: Leader properties for multiline text incorrectly displayed only one line. This is fixed.
Render: Alpha channel incorrectly contained transparency information when "transparent background" was not selected. This is fixed.
Render: When Rhino did not have focus, the render calculated was wrong. This is fixed.
Save:GHS: A crash bug has been fixed.
Save:STL: A crash has been fixed.
Save:STL: A problem with some objects not meshing properly has been fixed.
Split: Several failure bugs have been fixed.
Splop: A crash when the surface is a block insert has been fixed.
Sweep2: Weighted points are respected in any combination if the curves are otherwise also set up for Simple sweeps. Simple Sweeps to rational rails also accurately follow the rails now.
SynchronizeViews: The viewport display as set with SynchronizeViews was not saved. This is fixed.
Text: Text in a block object did not display properly if the block was rotated to another plane. This is fixed.
Toolbars: Rhino flyout toolbars did not work properly with Wacom Intuos tablets. This is fixed.
Trim: Several failure bugs have been fixed.
Trim: Several failure bugs have been fixed.
UnrollSrf: A failure bug with trimmed and flipped surfaces has been fixed.
UnrollSrf: Curves could be incorrectly split. This is fixed.
ViewportProperties: The wallpaper bitmap was not updating properly after a change to the bitmap file. This is fixed.
What: New information added - edge and vertex tolerance.
Worksession: The state of child layers was not correctly restored with the worksession file. This is fixed.