Connection String and login problems?

After posting and solving the last problem - I thought I'd post this one as it has got me a bit confused?

I am trying to connect to a local SQL Express database via an ASP website using the below connection string

Provider=SQLNCLI;Server=.\S15XXXX;Database=thenameofdb;Trusted_Connection=yes;

But I am getting the following error...

Microsoft SQL Native Client
Cannot open database "thenameofdb" requested by the login. The login failed.

I thought as I am using a trusted connection I didn't need to login? Have I got the connection string wrong? any help very much appreciated... Thanks
All sorted...

I just needed to add IUSR to the DB