When I tried to set up an ODBC connection to our QT4.1 app deployed on the production server it gave me two problems.

The first was an "QOCI can't logon" error.
I used the free Microsoft dependency checker and discovered that the application was calling for a dll which Standard Oracle Client didn't supply. It was missing a DLL that IS in the InstantClient10g:

The Oracle Standard Client for 9i does NOT contain oraociei10.dll but when our admin did a file search on his PC he discovered that it was present in the windows instant client that was installed along with the Oracle "Raptor" application, which is now called "SQLDeveloper", which is a free IDE.

I copied that dll to the
directory and when I tried the app I got an ORA-12705 error - something about an NLS problem.
So I added
to the environment and set it to
and the hap2006 app now runs beautifully!

If the workstation does not have the Standard Client installed the InstantClient works beautifully.