You will find how to set permissions here when you get it sorted..
http://technet.microsoft.com/en-us/library/bb727037.aspx
Have a read of the above link re Vista File and Printer Sharing.
How to give Permissions are there, too.
If you are running Norton, Trend Micro, McAfee, etc’s Firewall, check its
settings to make sure it allows file and printer sharing..
1st thing to do is make sure that the Workgroup Name of ALL the computers is
the SAME.
In Vista Network and Sharing:
Network Discovery: ON (So it can see the other computers)
Network set to Private (Public is for hotspots, airports, etc)
File Sharing: ON
Public Folder Sharing: ON (Vista’s Public Folder is the same as XP’s Shared
Docs)
Password Protected: OFF (unless you want to set up identical usernames and
passwords on ALL computers in your Network) If you have it ON, you will be
asked for a username and password when you try to access a Vista computer
from an XP computer.
Also, run the XP’s Home Network File and Printer sharing Wizard.