Check the registry to see if an Oracle client is already installed:
Computer\HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Oracle
or (64-bit):
Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Oracle
Download ODAC from the Oracle website and run the installer from the extracted folder:
install.bat asp.net4 c:\oracle odac
Oracle.DataAccess.dllwill be located atodp.net\bininside the installation directory.