I have a desktop and my daughter has a laptop, both running XP Home. I bought a Belkin wireless Router/Modem and a Belking USB wireless adapter (for the laptop). The router/modem is connected to the phoneline and via a network card (which was built in to the motherboard) to the desktop pc. Installed the appropriate software, ran the Belkin wizard and Voila! It works, it does what it says on the box and cost about £105 from Curry's. You can get it cheaper, I'm sure.
ps I'm not a great techie.