Folder Security

XP is designed to be a Windows Network Client.

Security is controlled by user accoutns and their associated passwords.

If you want to password protect a "folder" in the share you can zip it up and give the zipped folder a password. WIndows will then treat the zipped file like a folder but will ask for the password to open the "Folder"(zipped folder and files)

Alternativeley you could create Local User Accounts , on your computer, for the people you want to grant access to. Then you could add there access based on their account name.

The problem with this is they need to be the same as the username and password they are using on their own computer or they will be prompted for it when they attempt to connect.

Or they cam map a drive letter to your share and "connect as a different user" and provide the username and password of an account already existing on your computer.

Of course the Official Microsoft Solution is :

You need to install a Microsoft Server on your network to handle network security. And of course purchase all of the associated OS license fees and Client Access Licenses