Vista - Public Folder Sharing

Hi,

I'm on a home network. Its all been configured. My firewall has been configured. Just wondering how to put files in the public folder. I understand you can just copy files in there but i dont want to because it'll take up space. Is there a way to make individual files or folders share themselves into the public folders without duplicating themselves from the original to save space? Because i dont want two from the same file, ie one in the public folder and the other in the original folder.

Also, i use vista and my other network computers are on xp. I noticed on one of them, i can give it files and but i cannot take files from it onto my computer. I understand it must be a sharing setting on that computer but im not sure where to go to fix it since its xp and im a vista person now. If someone could assist me in those two issues would be greatly appreciated.