>while using a connect string w/o any problems with Windows Forms, I cannot use the same string with a Web Form. I get this error message:
>System.Data.SqlClient.SqlException: Login failed for user 'NT AUTHORITY\NETWORK SERVICE'.
>
>What kind of security I need to change in SQL server?

The difference is that Web pages by default run under the anonymous account (i.e. IUSR_XXXXXXXXX) and not the logged in user.
If you want each user to access SQL Server with it's own account, you must turn Impersonation on thru the Web.config file.
Otherwise, you may assign a domain user to the Web site anonymous login (thu the Internet Services Console), and grant permissions to that user on the SQL Server.

Hope this helps and bye
Jose