Recetly we had an issue for opening the SQL server enterprise manger in SQL server 2000 by customer and even for us also ->below is the error-

A Connection could not be established to <XXXXXXXXXXX>.

Reason: Invalid attribute/option identifier.

Please verify SQL Server is running and check your SQL Server registration properties (by right-clicking on the <XXXXXX> node) and try again.

Below are the solution which we have worked for the resolution-

1.Reinstall MDAC  to see will that fix the issue.. -No its not fixed

2.Reinstall the client tools alone ->no it didnt worked…

Then the only option we didnt try is to sqlsrv32.dll. so here what we did that
 we have checked in other working machine with the same Image of existing issue one we have renamed the current one to sqlsrv32_old.dll then we have copied to the path


so then it worked for us everything…

so be aware that-
1.While reinstalling MDAC better to stop the SQL server services so that it can link to all other sql as well.
2.Ensure you shouldnt play with the DLL files….