well you will have to do more then configer it in the xampp config file you will have to set up a dns server.
i guessing you have bind installed if you do read a guide on how to set it up
and may i sugest buying a proper doamin mane u think namecheep.com are the cheepest
for the guide and extra help i sugest going here
http://forums.devshed.com/dns-36/bet-yo ... 41940.html
and use the section that that post is in to ask your questions.
i can run a domain wihtout setting it up in the config files maybe theres a reason but i dont know it