I'm not what this is called so I don't exactly know what to search for to do my homework. But I have two IBM T40's and only one wireless internet card. I don't have to money to buy another wireless card, so my question is this: Can I use the card on one system and use an ethenet cable linked between them and use the internet on both pc's? And please don't tell me to just use a wired connection. I would be using this connection in my upper level of my house; my wireless router is in my basement.

I believe a cat5 crossover either network cable may work.

So a wired connection between the two T40s is required, yes, and the one with the wireless card should be set up to route traffic from the wired interface over to the wireless one. There are various setups you could use; the ipmasq Debian package comes with a simple iptables (IIRC) configuration which accomplishes this, or you could set up a bridge.