For Windows 7 or 10, I'd like to connect a computer to WiFi router that is internet-connected while also being connected to a second WiFi router that is not internet-connected.
The purpose of the offline WiFi is for WiFi-based file transfers between devices.
Is there a way to do this?
From the comments and further testing, a specific solution on a Windows 7 or 10 machine with built-in WiFi hardware is the following (assuming two different routers to connect to):
1) Attach and install a second WiFi adapter (i.e.: a USB-to-WiFi device). Power on a second WiFi router.
2) Go to Network Connections, disable the original built-in WiFi hardware, enable the second WiFi adapter.
3) Connect to the second WiFi adapter to the second WiFi router connection, then re-enable and connect the original WiFi hardware back to the first WiFi router connection.
From there, one should be able to have two simultaneous independent WiFi connections across two different routers.