Could not load file or assembly 'Oracle.DataAccess' or one of its dependencies. An attempt was made to load a program with an incorrect format

It seems the Oracle Data Access Component installation process using the "11.2 Release 3 (11.2.0.2.1) with Xcopy Deployment" version is broken. To fix this you must register the missing assemblies in the GAC. To do this for this specific version run these commands from within an administrator console:

md C:\Windows\assembly\GAC_32\Oracle.DataAccess\4.112.2.0__89b483f429c47342\copy %ORACLE_HOME%\odp.net\bin\4\Oracle.DataAccess.dll C:\Windows\assembly\GAC_32\Oracle.DataAccess\4.112.2.0__89b483f429c47342\md C:\Windows\assembly\GAC_32\Oracle.Web\4.112.2.0__89b483f429c47342\copy %ORACLE_HOME%\asp.net\bin\4\oracle.web.dll C:\Windows\assembly\GAC_32\Oracle.Web\4.112.2.0__89b483f429c47342\

Note that this registers only the DLL's but not other languages resources. So, if you are using any another language than English (de, es, fr, it, ja, ko, pt-BR, zh-CHS, and zh-CHT), then you need to register these as well using the corresponding resource file.

If you have Visual Studio installed on the machine, you can issue the following commands instead:

gacutil /i %ORACLE_HOME%\odp.net\bin\4\Oracle.DataAccess.dllgacutil /i %ORACLE_HOME%\asp.net\bin\4\oracle.web.dll

Note: look for gacutil.exe under the Visual Studio installation folder for it.

Hope this helps.

P.S. Or you can try this.

I avoided registering the 11.2 Release 5 assemblies in the GAC by setting "Enable 32-bit Applications" for the application pool to true.

You may need to enable 32-bit applications in your AppPool.

http://www.alexjamesbrown.com/development/could-not-load-file-or-assembly-chilkatdotnet2-or-one-of-its-dependencies-an-attempt-was-made-to-load-a-program-with-an-incorrect-format/