Hi,
if you're inside a Windows Active Directory Domain (which I assume), you will have to go to the IIS settings of the Web Server hosting your SSRS Web Site.
This is typically achievable via the Computer Management Console (right click "My Computer", choose "manage"). There open the tree Services and Applications -> Internet Information Service -> Web Sites -> Default Web Site (or your special SSRS web site) -> Reports.
Right-Click Reports and choose "Properties", choose the tab "Directroy Security", click the Button "Edit" under "authentication and access control" and check the "Integrated Windows authentication". Leave all other checkboxes checked. Maybe you'll have to clear the "enable anonymous login", but that should be disabled anyway.
This allows you to get to the reports without login, if you a re using Internet Explorer as a client. It does not work, however, with Firefox; for him you still need the "basic authentication", which asks you for the login name.
Just a guess...
Guenter