You stated that you bought 50' of cable. You made no mention of a switch or hub! You can't connect 2 computers together using regular cable. If you don't want to buy a switch or hub, you need a crossover cable. This type reverses wires 1-3 and 2-6, so that the receive on one end is connected to the transmit on the other.
Otherwise, get a switch. You'll get much better performance than with just a crossover cable or a hub.