xp Pro will only give you simplified file sharing. If you wish to access permissions you must be networked as a domain. If you wish to set permissions because you have multiple users using the same computer you can set the user type facility.
By default, other users do not have access to your files unless they are in the group administrators.
If you wish to limit the permissions of users
Logon as an administrator
Open Control Panel
Select User accounts
Double click on the user account
Change the account type to limited
Click on Change account type.
If you then wish to share files with these users you can set up simplified file sharing and drag any files you wish to share to the shared folder.