How Does Databse Driver Manager Know The Application Is Unicode Aware ?

Hi, all:

My VC6 MFC application is recognized as a Unicode application by the driver
manager, so when I read nchar fileds in MS SQL Server database, the
SQL_WCHAR does not convert to SQL_CHAR, and the application ASSERT failure
at CRecordset::GetDefaultFieldType function.
But I don't have "_UNICODE" defined, and have no "W" suffix functions
called, and my old version program compiled on Feb 2004 just work fine.
(source code lost unfortunatally)

I read docs like:
http://msdn.microsoft.com/library/d...ver_manager.asp
http://msdn.microsoft.com/library/d...ode_drivers.asp
but can't find the right answer.

Could any one tell me how dow the driver manager judge the application to be
Unicode aware?

Best Regards,
Qiang He

(remove the "nospam." to email me, thanks)