Which Windows XP do you have. Professional or Home Edition?
If you are running WindowsXP Pro disable Simplified sharing. Then right
click your folder and select properties. You will see Security tab where you
can assign who has permission to access the folder. Note: Partition on which
your folder resides has to be NTFS formatted. http://support.microsoft.com/default.aspx?scid=kb;en-us;307874