Windows 10 (x64) or higher is required to run Proclaim on Windows. Running an earlier version of Windows will cause Proclaim to show a banner recommending a Windows update.

If you are running Windows 10 and see the banner anyway, it's possible that you're running Proclaim in Compatibility mode.

Compatibility mode is Microsoft's way of allowing you to run older programs on newer operating systems. Proclaim, though, needs the newer versions of Windows to run properly. Running it in Compatibility mode may work fine, but you also may be informed that you're running an older operating system than you actually are.

To see if you're running Proclaim in Compatibility mode, locate the Proclaim icon in your desktop or toolbar.

Right-click and select Properties, then click the Compatibility tab. Uncheck the box and click Apply. Relaunch Proclaim, and you shouldn't get any more notifications that you're running an unsupported version.