Problem with Samba

With the Samba package installed I can view and download files from a Windows box to the Ubuntu box. When I try to connect to the Ubuntu box from a Windoz box it asks for a user name and password. I put these in the dialog box but it still will not connect. What am I doing wrong. I can see the linux box on the Windoz network but it will not connect. Also if I want to share a printer which box would it be better to install the printer the Linux or Windows. Any help would be appreciated. Thanks in advance.