Q: Can I install REFPROP 9.1 on Windows 11?
A: Possibly, but it is not officially supported. Users report success using Windows 10 compatibility mode (right-click installer > Properties > Compatibility > Run as Windows 10).
Q: I lost my license file. Can NIST reissue it for version 9.1?
A: Likely not. NIST strongly encourages upgrading. If you have proof of purchase, contact refprop@nist.gov – but be prepared for a “no.”
Q: Does REFPROP 9.1 include mixtures?
A: Yes, it supports binary and pseudo-binary mixtures. Use the “Mixture” menu in the GUI or the REFPROPm DLL.
Q: Why does the installer ask for a disk 2?
A: Some CD distributions of REFPROP 9.1 span two disks. Download the full ISO or copy both disk images to the same folder.
Q: Is there a silent install for enterprise deployment?
A: Not natively. You can use AutoIt scripts or response files if you extract the MSI using Universal Silent Switch Finder.
Here is where many refprop 91 install attempts fail. You will see one of two screens:
If you no longer have your serial or license file, unfortunately, you cannot complete the installation. Contact NIST’s REFPROP support, but note they may not support version 9.1 in 2025.
Cause: Permissions issue with Windows Registry.
Solution: Run the installer under the hidden Administrator account. Enable it via:
net user administrator /active:yes
Then log out and log in as Administrator to run the installer.
Even following the steps perfectly, you may encounter errors. Here are the most frequent issues with refprop 91 install and their solutions.
Locate the Setup.exe file. Right-click and select "Run as Administrator." If User Account Control (UAC) prompts you, click "Yes."