The main PC that connects to the ADSL will require a wireless ADSL router and Internet Connection Sharing and the Laptop will require a wireless PCMCIA card so that the two can talk to each other.
If you have WinXP on both systems, setting up a home network is quite simple...
Just insert your WinXP disc where you can run the setup from there... I think it is in the main menu when the CD auto boots...
Select "Perform Additional Tasks"
Select "Setup a Home or Small office network"
Follow the instructions, create a floppy which you use to install the settings on each additional PC, do as it says, reboot all PC's and that should be it.
You may have to allow the home LAN to connect to the internet thru your Firewall... and then after many hours of pilling your hair out, shouting and swearing... you should be able to connect to the internet/LAN
It can be a bugger at times.... so Google your problems or use this URL:
http://www.homenethelp.com/If ya get stuck give me a shout!
Good luck!