Summary: How to fix the Installation Error 5100.
Related installation help: Troubleshooting Rhino 5 Installation
According to Microsoft, the 5100 return code is related to system requirements.
Reboot the computer.
If the previous setup required a reboot, it may not have finished. After this reboot, the .NET Framework 4 setup should be installed.
Does the target system have enough hard disk free space? The .NET 4.0 minimum requirement is 2 GB disk space for installation. Free up space in the installation drive and installing it will work fine.