Hey, that's good news -- XP is simple to bridge adapters.
Just go into the network control panel advanced adapter settings, highlight the wired and wireless adapters, right click and select bridge selection. Then the two networks (one on the wired and one on the wireless) will be available as one and share the Internet connection.
HERE is a brief Microsoft guide to doing it.
Actually, I'm the one in over my head today. I installed FreeDOS on an old Shuttle machine to run some real picky DOS-only Haltech automotive software and I'm trying to recall all the syntax from years ago to install some previously unavailable DOS USB drivers.