how do i network xp with a vista and acces xp files?can i have a step by step instructions.thanks a lot.?

i have to laptops,xp and vista.i dont have a router.and buying isnt my type.so im planning to use my wifi connection to network the two.and acces the files.i know how to "ad hoc" but only when the host is the vista.how do i share my xp's internet connection? thanks for the help.