SQL server access failed at runtime...

If you use windows login this is how the connection string should be
"server=localhost;database=Northwind;Integrated Security = SSPI"
If you use SQL Server login
"server=localhost;database=Northwind;uid=sa;password=sa"
Since your sql server is on a different machine , where both the machines are on the same domain, and you are using windows authentication, your windows user account should be added to the sql servers users with adequate permissions, Also while defining the SQLConnection if you specified a user name try specifying domain\username in case of windows

What level of authentication is your ASP.NET application using? Are you attempting to use a trusted connection with SQL Server?

i am sorry, i am very new to this technology. I dnt even know what r different levels of authentication and what is a trusted connection. can u help me giving me any reference to resources regarding this?

it worked now. the problem was in connectionstring property, password was not there. infact, i mentioned user name and password both during setting up my dataadapter. but afterwards, in properties box, i saw it was missing!!

can u suggest me some resources to study on different levels of authentication in detail?