can you connect through the sqlplus, go to the dos prompt and type sqlplus.

sqlplus user_name@tnsname_alias

Could you confirm this?



Here is a NOTE from metalink:

Problem Description:
====================

Getting an ORA-03121 trying to connect on Windows NT.




Keywords: 32,winnt

Solution: CONFIRM THAT SQL*NET IS INSTALLED ON THE WINDOWS NT MACHINE


Solution Description:
=====================

Check to see that SQL*Net is installed on the Windows NT machine. Look for
the SQL*Net product in the orant\orainst\nt.rgs file.

If SQL*Net is not present, it must be installed at this point.

If SQLDBA can connect but 16-bit Windows based applications (SQLPlus,
SQLForms, Reports, Oracle PING, NetTest, etc.) installed on a Windows NT
machine are returning an ORA-03121 error, then verify that SQL*Net for Windows
is installed on the NT machine as well.

You can also get the ORA-03121 error using an incorrect connect string. The
correct syntax for connecting to SQl*Net Version 1 for these protocols
are:

TCP/IP t:hostname
Namedpipes p:service:

If you are trying to connect on NT using a Windows Based Application on NT
review the ORA-3121 bulletin for Windows.






Solution Explanation:
=====================

Windows NT and OS/2 have the ability to emulate Windows.

In the case of OS/2, this emulation is referred to as a WIN/OS2
session. SQL*VDM, a product developed for OS/2, will enable 16-bit
Windows based products to connect from a Win/OS2 session to the
regular OS/2 session.

On Windows NT, this product is called Windows-ON-Windows or WOW.
Unfortunately, there is not a product such as SQL*VDM for Windows NT.
In order to connect from Windows-On-Windows (16-bit), you must have
SQL*Net for Windows (16-bit) installed under the orawin default
directory for Windows on the NT machine.

SQL*Net for NT is a 32-bit SQL*Net product. It can only be used by 32-bit
applications such as, sqldba71.exe.


Sam

[Edited by sambavan on 09-10-2001 at 12:27 PM]