Can an old FSX install be reactivated after windows reinstall?

I see there is a FSX registry fix but I don't know of all the situations where you may use it.

Every now and then I reinstall windows, usually because of some silly problem that can't be resolved otherwise - I am a tinkerer.

At some point I have to re-install FSX which is a pita with the addons as well. Will something like the registry fixer allow me to bring the old install back to life?

Thanks,

Jason