This chore, which was easy in earlier Windows versions, is difficult and poorly documented in XP Professional and theoretically impossible in XP Home. But there's a workaround: When someone accesses your computer over a local network, XP provides access through the Guest account, even if that account is turned off. So if you password-protect the Guest account, you effectively password-protect network access to your PC.
On your XP system (which I'll call the "host"), select Start, Run, and type net user guest password, replacing password with something less obvious. Press Enter and reboot your system.
From now on, visitors trying to log on to the host from another PC will run into a dialog box asking for the password. Without it, they can't log on. There are a couple of caveats, however.
First, visitors must first access your PC through Windows (rather than through an application), which opens a password dialog box automatically. They won't be able to access the folder on the host through another program until they've done so with Windows Explorer, the desktop, or another Windows resource.
Second, the host's Guest account must be turned off--that's the default setting. If it's on, select Start, Control Panel, User Accounts, Guest, Turn off the guest account.
