In a nutshell, the user account that you use to connect to that machine doesn't have permission to access it. When you first connected, Windows will have prompted for a username and password. These credentials need to originate from the remote machine (TAMMY-PC) and not yours.
In other words, if TAMMY-PC has a username and password of
tammy, then you'd use
TAMMY-PC\tammy as the username and
tammy as the password.