We've been deploying a BizTalk 2006 solution to a x64 system and, while BizTalk 2006 itself has no problems, I've had a lot of problems related to the BizTalk Adapters for Host Systems and the BizTalk Adapters for Enterprise Applications.  I plan to write a number of posts in the near future discussing these problems (once we have them all resolved).  In the meantime, I wanted to share this little tidbit I've learned about ODBC on 64-bit windows.

It's important for you to know if your application is going to run as a 32-bit or 64-bit application.  There are two different repositories for ODBC connections, based on the drivers you've installed and the client that will run them.  32-bit applications will only see ODBC connections from the 32-bit side, and 64-bit applications will only see ODBC connections from the 64-bit side.

32-bit applications register ODBC connections to the following registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\ODBC\ODBC.INI

64-bit applications register ODBC connections to the following registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\ODBC\ODBC.INI

Adding these keys is initially tricky, but if you understand the above then it should make sense.  Typically, you go to Start --> Administrative Tools --> Data Sources (ODBC) to create your ODBC connections.  And this is fine if you want to create 64-bit ODBC connections.  Any ODBC connection created using the Data Sources (ODBC) link will get created in the HKEY_LOCAL_MACHINE\SOFTWARE\ODBC\ODBC.INI key.  This is because it calls the program %WINDIR%\System32\odbcad32.exe.  However, this program will not create 32-bit ODBC connections.

To create 32-bit ODBC connections, you have to run %WINDIR%\SysWOW64\odbcad32.exe.  Adding an ODBC connection through this application will create the ODBC connection in the HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\ODBC\ODBC.INI key, and allow your 32-bit applications to see and use the ODBC connection.

I'm still getting used to the concept of WOW and how it runs 32-bit applications on an x64 system.  This information may not be news to some of you, but it presented a challenge to me.

I hope this helps!