Here you can download older versions of Nexus, Nexus Ultimate and Winstep Xtreme up until version v16.9 (previous releases were not archived)...
Running older versions is not recommended since they may lack support for newer builds of Windows or they may have stability issues that have long been detected and fixed.
Click the application name to download the setup file. Click the release date to view the announcement page with full details.
How to determine which version to download
To determine the last version that will run with your license key, refer either to the original registration email or to the text at the bottom of the About tab in Preferences, both will say something like "THIS LICENSE KEY IS VALID FOR ALL [product] updates released, or to be released, until [date].
With this information at hand, scan your product related table for the last version released immediately prior to this date.