Um let take for instance you are using window xp since that was not specified on here .
from pc A we will need to set up Ad hoc and to go about it .
from the desktop or control panel locate MY NETWORK , click on setup wireless connection, and you will be prompt to enter ssid name , give it any name and enter your wep key and make sure you dont forget the password which is your wep key.
follow the connection up and click on finsh .
Now on the other pc which is pc B , You make sure you have wireless card on the pc , scan for wireless network around you, which you should see the name which you entered as SSID, double click on that and its going to ask you to enter your wep key, do enter that .
before you know it , Both pc are connected .
Please let us know which Operating System are you using on both computers,the
settings and configuration may vary if both computers having different windows
or operating systems. Yes you need wireless NIC Cards in your both computers otherwise you must be having a built in wireless NIC Cards in your both computers.