My router has a pretty descent firewall so i feel like it should be safe? Maybe. Obviously I won’t be signing into any online accounts or anything like that on the XP machine. Is this a bad ideas? Obviously using Windows in general is a bad idea but I’m sort of limited by the hardware here.
If all you are going to do is play old stand alone games why are you attaching it to a network?
Just sneakernet the install.
I would not attach an XP machine to a network.