The easiest way is to edit /etc/hosts - the syntax of the file is self explanatory. If you want to go over the top in the future then setup your own DNS. There is almost never a need to do so on a home LAN, infact you'll probably just waste of your time getting it to work... Hence why I run one
More to play with!
If you need to do the same for Windows9x (and probably ME) then create c:\windows\hosts in the same fashion. On WinNT/W2K its under c:\windows\system32\drivers\etc\hosts - obviously!!
HTH
Jamie..