The solution of this error
SharePoint 2010 error: Retrieving the COM class factory for component with CLSID {XXXX-XXXXXXXX-XXXXXXXXXXXx} failed due to the following error: 800703FA
This error come when you create a console application with reference of Sharepoint dll, and when you default create a console application, it generate the exe in x86, but if your sharepoint is 64 bit it wont work, So change the build configuration for your console app for x64 bit.
