Someone has given me two boxes, never opened, of something called NETGEAR. It says on the box it is a PCI ADAPTER CARD and apparently is used to hook two computers together.

Anyone have any more information on this - any pitfalls? Is it just something I can PLUG the cards in with and go?

I know nothing about this facet of computing.It sounds LIKE an Ethernet card. You may alread have one in your computer. If you have one, you don't need another. If you don't have computers networking, you don't need it either, unless you are going to start cable/DSL modem.Maybe if you provide some more info such as what is printed on the box such as a serial # and or model # we wouldn't be sitting here GUESSING...

Netgear

PCI ADAPTER CARD

Share your internet account, files, and printers among multiple PCs with your existing HOME phone line

Make EVERY telephone jack in your home an internet connection

No new wires to install
LED displays

Model PA 301

PC 32-bit PCI Bus

Most of the stuff on the box.

I don't have DSL and can't get any kind of broadband out here in the country, but if I could use this to play games between two computers, that would be neat.

Thanks in advance.You will have to check if either machine already has an Ethernet card as both machines will need one if you are going to network them together.
Then all thats required is a crossover cable and a visit to ezlan.net for some reading up on setting up a home network...

patio.  That may not be an ethernet card, but a phone line solution. These were made a few years back and I think they transmit at 1, and no more than 10, so unacceptable for what you are planning (like gaming). The old ones were originally made by Diamond Multimedia, I believe.