For internationalizing an MFC application, it sounds like there are two main approaches:
Compile and deploy resource-only DLLs. Extract and replace all strings with the localized version.
References
Internationalization in MFC Internationalization in your projects Localization and internationalization, what's the difference? appTranslator localization tool: Costs $460 and $630 for standard and professional editions. This generates a separate EXE for each language. Internationalization & Localization: an article that gives an overview to i18n of software.