Networking 2 x XP Computers

I have 2 Computers running Windows XP with 2 x Realtech 10/100 ethernet adapters connected by one rj-45 cable. One computer is a Pentium 4 with 512Mb RAM and 80Gb HD and the other is a Pentium 3 with 128Mb RAM and 12Gb HD. Is it possible to networkthese two computers without buying a hub? I have been using the wizard and cannot get them connected. They can detect when the other is connected or disconnected but I cannot share any files. Any suggestions would be much appreciated!