Wireless networking is SLOWER then conventional Ethernet cards. It also introduces security issues, as anyone within range, could potentially access your machines, so enabling encryption is a must.
As far as I know, AOL does not support Internet Connection Sharing (ICS) so click here for a thread that explains a work around.
Before attempting to share the internet, it is essential you get the network working properly first. Look at XP's Help Files, which will explain how to use the Network Wizard to set the network up.
The cheapest option would be, two network cards (if they are not already fitted) and a CROSSOVER cable to connect each card directly to each other. Many modern machines have a network capability built into the motherboard, so check your manual.