It is seen that Windowsx64 Edition Operating System has following two directories:-

It is seen that Windowsx64 Edition Operating System has following two directories:-
1. Program Files
2. Program Files(x86)
Windows XP Professional x64 Edition redirects the \Program Files directory for all programs that are 32-bit during the installation to the \Program Files(x86) directory. Programs that are 64-bit compatible are installed into the \Program Files directory.
The \Windows\SysWOW64 directory is where 32-bit system files are installed. 64-bit system files are in the \Windows\system32 directory for compatibility reasons.
For a 64 bit Operating System, Microsoft offers a set of 32 bit executables in the WoW(Windows on Windows) directory of the system.

To setup DSN for 32-bit application you must use:
%WINDIR%\SysWOW64\odbcad32.exe

and for 64-bit application you must use:
%WINDIR%\System32\odbcad32.exe

So, to run a 32 bit application, we would need to modify the env PATH variable and put SysWOW64 before system32.

Roughly the steps would be
1. Start %windir%\SysWoW64\cmd.exe
2. Set PATH=%systemroot%\SysWOW64;%PATH%
3. Run the application.
4. After application has completed, reset PATH variable if required.

If the application can't be run from a shell then you could modify the PATH variable directly from System Properties > Advanced Tab > Environmental Variable > System variable.

Edit the PATH variable accordingly and reboot the system for the changes to take effect.