How can I network my Vista laptop with my XP SP3 desktop?

I have a custom-built PC desktop with a wired broadband modem. My HP laptop has a built-in WiFi card in it, so it picks up the internet, but I’m not sure how to set up a network so I can share documents between the two computers. My Google-fu has not led to much success in getting instructions in plain English on how to network these things or without me having to join some forum that costs money.

How do I get these two crazy kids together?