The client can connect to. Net programs and cannot connect to SQL Server 2000

Working Machine (ASP. net Program ,. net Framework 1.1) in the domain, the SQL 2000 server is not in the domain, and suddenly the SQL Enterprise Manager and query analyzer can be connected to the SQL 2000 Server. if the SQL Server does not exist or the access is denied ".
It seems that I have used it like this before and there is no problem. It seems that it may be related to the domain control policy. During this time, the company's domain policy adjustments were frequent, mutual access between machines without login domains and machines in the domains is getting worse.
After a while there was no result, I guess it may be that the account used by ASP. Net cannot be verified by the SQL 2000 Server. In fact, I still don't doubt this, because the Client uses network port (default port 1433) communication when connecting to the SQL Server, and does not need user verification of the operating system of the Server where SQL Server is located.
 
The test is as follows:
1. My domain account has full access to machines that control SQL 2000 servers. In the C: \ WINDOWS \ Microsoft. NET \ Framework \ v1.1.4322 \ CONFIG, put the machine. in the config file, change the userName of the processModel node to my domain account, set the password to the password of my domain account, restart IIS, and log on to the system. In the task manager, the startup user of the asp_net process is my domain account.
2. Create a Windows Account ASPNETTest on the working machine and add it to the Administrators group (note that the password must be changed when the account first logs on to the system) and set the password (for example, qazQAZ123 ). Change the machine. CONFIG username of C: \ WINDOWS \ Microsoft. NET \ Framework \ v1.1.4322 \ config to ASPNETTest, and set the password to qazQAZ123 ). Create a Windows Account ASPNETTest on the SQL 2000 Server. Set the password to qazQAZ123, which is the same as that of the working machine, and add it to the Administrators group. Restart IIS and log on to the system. In the task manager, the startup user of the asp_net process is ASPNETTest.
 
In Security of SQL 2000 Server, SQL Server and Windows are set. If the above test has something to do with this, it cannot be said. The SQL Server authentication method is specified in the connection string of the program. If the SQL Server account and password are incorrect, the SQL Server cannot be connected, in this case, both SQL Server Authentication and Windows authentication must pass.
In addition, ASP. Net sends the account and password authentication information used on the work machine to the SQL 2000 Server for Windows authentication, which is strange. Is ASP. Net doing this, or is the domain security control policy leading to a Windows authentication process?