I have a small network of mostly old PCs but I do have a Windows 7 and a Windows 10 PC now too.
When I open a web browser and go to: http://192.168.0.109:8080 my FlightAware works only on Windows 7 and 10 PCs. No longer does it work on Windows XP PCs.
Well, I should have written something with the screenshot I posted. My mistake.
I just wanted to show you that there is no problem with XP or with the address. I get the SkyView on XP by typing both ways, with or without http. http://192.168.0.21:8080
or 192.168.0.21:8080.
I do not understand the reason why you dont get it on XP.
What browser are you using?
I see from the screenshot that @abcd567 is using Firefox. If you are using the original XP version of Internet Explorer it is possible it is not compatible.