XP Folder Sharing

This will only work in windows XP - Professional.

Start the Microsoft Management Console (MMC) Local Security Policy snap-in (Start, Control Panel, Administrative Tools, Local Security Policy).
Expand the Local Policies branch.
Select Security Options.
Double-click "Network access: Sharing and security model for local accounts."
Select "Classic - local users authenticate as themselves", and click OK.

Now share the folder

Open up the sharing and security tab (Right-click on the folder to share and select Sharing and Security...).
Share the folder over the network (Click on Share this folder)
Add users that can gain access to the folder (Click Permissions)
To only enable certain users remove everyone.
Add specific users (click Add, Advanced, Find Now)
- to add all users on the computer select Authenticated Users
- to select multiple users at the same time hold down Ctrl
Click OK and then select the amount of access to be granted to each user.

Troubleshooting

Start the Microsoft Computer Management Console (Start, Control Panel, Administrative Tools, Computer Management).
Expand the System Tools branch.
Select the Local Users and Groups.
Double-click on the users folder.
Make sure that the account names match the login names.