Hi Vijay,
According to your description, when typing in the URL "http:// computername/reports",
the browser prompt you to login, right?
In Reporting Services, if you don't use NTLM authentication and visit Report Manager out of domain, you will be required to enter your username and password. In your scenario, are you visiting Report Manager out of domain? If so, please check the rsreportserver.config
file authenticaiton type is Negotiate or Kerberos under "C:\Program Files\Microsoft SQL Server\MSRS12.MSSQLSERVER\Reporting Services\ReportServer". It's because that Negotiate attempts Kerberos authentication first, but falls back to NTLM if
Active Directory cannot grant a ticket for the client request to the report server.
If the authentication is not NTLM, you can try to change the report server authenticaiton type to NTLM. And then when visiting Report Manager, you don't need to enter your account.
If you have any other question, please feel free to ask.
Regards,
Shrek Li