The older PC must have a wireless card or suitable USB stick and that is 802.11 technology unless you have some ancient box using something propriety which I doubt.
If you mean it is G wireless then it will work fine. G wireless is compatible with N wireless and can handle WPA2 AES security as long as you have XP SP3 at least.
If it is B wireless or earlier than XP .. throw it and get another PC from your local PC ex-lease provider.. or something like that, and buy a USB stick for it.. total cost less than $100. Do not mix B wireless with modern units. it cannot handle WPA2 security or even WPA security for the most part.