What is the procedure for interfacing a wireless laptop computer with a desktop so that I can share files?
At its simplest the only hardware you need is a crossover-type ethernet cable plugged into the network connectors of each computer.
Make an accurate note of the name of each computer (Control Panel, System, Computer Name).
Go into My Computer on each machine and enable file sharing on relevant folders.
Run the networking wizard which will create TCP/IP (if it's are not already set up).
In Networking, turn off the firewall in each computer.
You then need to create a new Network Place (generally I run the Networking Wizard but your setup may be different).
Two things: Windows Help is some help if you get stuck. The add new Network Place routine can be slow and truculent -- if you are patient it should work eventually.