It's fairly simple to do, but do not... i repeat DO NOT start filesharing unless your wireless connection is encrypted in some way shape or form.
Leaving your network un-encrypted not only means that people can nick your files, but it also means people can put stuff on it.
Anywho, on XP. Right click the folder/drive you wish to share (Sharing a whole drive is not recommended though!!) then click "Sharing".
on your other computer, open up my computer then tools -> map network drive, then it'll give you a drop down list. Go to your network, and in there it will show your now shared folder/drive. Assign it a letter, then you will be able to explore that drive/folder from the comfort of the other computer.
