Create portable copies but save them to your hard drive. You want a portable copy for each language you know. Create shortcuts to each of these portable copies. Instead of running on flash drives, they simply run off your PC from their own directories.

You will also need a way to change the windows display and interface languages as well, or you're going to have German NVDA trying to read English! There are ways to do it -- talk to Microsoft support or look through their knowledgebase to get assistance. Microsoft also has two disability support portals: one for home users and one for enterprise users. You can ask these folks about easily switching your Windows language.

Remember Windows has an interface language, a display language a keyboard language and a speech language. You can set any or all of these. And you can switch between them.  Though the traditional "language bar"is a floating toolbar that NVDA cannot read, the keystrokes to switch languages are accessible and you don't really need to access the language bar to do the switching. I'll be discussing this in my NVDACon talk this Saturday.