For 64-bit Windows, you can install the windows msi here. Newer Windows systems may complain about .msi files, but we don’t have an alternative at this point.
Alternatively, popupCAD source code can run on Windows, Mac, and Linux. Please check out their respective pages for more information on how to install the respective code bases. Please contact us with any problems with the respective instructions. Variations in systems abound, and we are not likely to catch them all.