Cannot see Oracle ODBC driver in datasource administrator in Windows 64 bit

Problem:

I cannot see Oracle ODBC driver in datasource administrator in Windows 2003 64 bit.

Cause:

64 bit 32 bit incompatibility issue for odbc driver, data source administrator and application.

Solution:

I have Windows 2003 64 bit, Oracle 10.2 32 bit Client and 64 bit application.
After googleing around,

I found that there is two versions of odbc datasource administrator:

The default one, is 64 bit which we use Start menu for opening it.

In order to open the 32 bit version I used: %windir%\SysWOW64\odbcad32.exe.

With the help of 32 bit version datasource administrator, I could see my 32 bit odbc driver listed.

I extracted this rule of thumb: If your application is 32 bit, then your data source must use Oracle 32 bit client as well.

Last words, beware of 3 pieces:
1- your application (which uses DSN definition),
2- Oracle client
3-data source administrator

All pieces must have same version, in my case it is 64 bit and therefore I installed 64 bit client.

Further reading:
http://support.microsoft.com/kb/942976