An error occurred while registering the newly created SQL Server

I used SQL Server 2000 "Enterprise Manager" on the client --> when creating an SQL Server registration, I entered the IP address of the database server. When the registration failed, I was told that the database server I specified was not found.
In the upper-right corner of the pop-up dialog box, select the database server in the LAN with three small buttons (that is, enter the button on the right of the server IP address bar), but the name of the server is not found!
I have also installed n SQL Server 2000 database servers. This problem occurs! I was depressed for two months.
Recently, I suddenly remembered that the SQL Server 2000 Server did not install the SQL Server 2000 sp3 patch, and the problem was solved!

In this case, we found that the SQL Server 2003 Service must be installed on Windows 2000 with the SQL Server 2000 sp3 patch. Otherwise, the database cannot be connected.
In the past, I installed SQL Server 2000 on Windows 2000 server. If I do not install a patch, I may be poisoned. If I am poisoned, I will remember to install a patch, but no matter whether I do not install a patch, it is very convenient for the client SQL Server 2000 "Enterprise Manager" to create a new SQL Server registration.
Maybe Microsoft is concerned with system security.
In addition, the client connects to the unpatched SQL Server 2003 Server on Windows 2000 without entering an IP address. You can directly enter the server name to register the connection and create databases and tables. I have never figured out this. Is this a vulnerability that Microsoft has not completed?