Summary: .NET Framework 4.0 installer gets an error while installing (exit code -2145124330)
Related installation help: Troubleshooting Rhino 5 Installation

Solution
Repair .NET Framework before installing Rhino 5.

1. Download Microsoft .NET Framework Repair Tool.
2. Run the repair tool.
3. Keep clicking the Next button until you get only one Finish button to click.
4. Install Rhino 5 again.

Note: If this repair tool doesn't fix the problem, you can also try the .NET Framework Cleanup tool.