Login failed for user COLDFIRE/ASPNET

i have my SQL server in windows integrated security so my connection string doesnt have to have password and uid stuff.
this is my connection string

data source=COLDFIRE;initial catalog=Northwind;integrated security=SSPI;persist security info=True;workstation id=COLDFIRE;packet size=4096

i tried this in windows form project of .net and work fine, i connected easily but when i tried it in asp project i got this error :

Login failed for user COLDFIRE/ASPNET

whats wrong with it?That's because the ASPNet user account, which was created when you installed ASP.Net, is not set up as a user on the SQL Server.