If the files you are trying to access are password protected, make sure that the account you are logged onto has the same password as the one set for these files. If you are not sure if they are password protected, go to the host computer (the computer sharing the files) open up the sharing properties dialogue box (right click) and it should tell you in there. The only other possibility is if the files you are trying to access are on another domain. In windows xp, if you click on the folder it should prompt you for a password and username. If the domain the files on are MSDOMAIN and your user name is sam, you would type MSDOMAIN\sam and then your domain password.