While attempting to install STPISecure, an error message is displayed:
STPISecure requires Microsoft .NET Framework 3.5.
Please use Windows Update / Windows Features to install this version, and then re-run the installer.
Solution:
Install Microsoft .NET Framework 3.5 through Windows Update or use the "Turn Windows features on or off" option from Add/Remove programs to enable .NET Framework 3.5.
Once Microsoft .NET Framework 3.5 is installed, retry installing STPISecure.