Windows XP introduced a new network security model called Simple File Sharing. Before I explain this, I'll give you some background. In the original Windows NT/2000 workgroup network security model, when you attempted to use a shared network resource, Windows would see if your username and password matched an account on the remote computer. One of four things would happen:
If the username and password exactly matched an account defined on the remote computer, you'd get that user's privileges on the remote machine for reading and writing files.
If the username matched but the password didn't, you'd be prompted to enter the correct password.
If the username didn't match any predefined account, or if you failed to ...