XP Pro supports multiple networks/network adapters. You can add a second wireless network adapter in the server and then set up a second network
- see here. You can either add a second router for the second network and connect both PCs through it, or set up
an ad-hoc network directly between the 2 PCs, though 50m sounds too far, I'd go for the second router which you can connect direct to the wired connection of your server.