Looks like you want:
A File server.
File servers aren't really supported by Windows XP Pro per se, however it does support File Sharing... and I believe you can add permissions for only certain people, but you need to add them to your own computer.
If you just want everyone to be able to store files, just set up a Shared Folder and everyone can get to it to put files into it.
To do that, go to My Computer, go to the drive you want to use, make a new folder. Right-click the folder and select "Sharing and Security."
Click "Share This Folder."
Then, you're done for now... that will allow everyone to access that folder.
I think it's possible but it's a royal pain to do. Personally, I'd just set up an FTP site on your computer and use that instead. If you want it to be private for each user, that is.
http://www.practicallynetworked.com/sharing/xp_filesharing/index.htm
Try that article and see if you can do it.
Windows XP Pro comes with Internet Information Services and that can be used to create an FTP site.