Princess -- get a router -- it splits the IP and you are all set. Be sure though, if you buy a "G" series router, you have a "G" series card. A "G" series router will work with other cards, but it is best to keep them on the same wave-length for best transmission of data.
5 machines here as well ... no biggie.
1- Mine (Linux boot)
2- Mine (WinXP - also now running as an FTP server)
3- Mine (Laptop - XP)
4- Wife's (WinXP)
5- Kids (WinXP)