Press Alt+Return to enter windowed mode in fsx. Hit windows key, and search for game controllers. Once the dialog box opens, leave it open and go back to fsx, and back to full screen if you wish.
Works instantly, meaning you don't lose your flight. It sucks especially if your on a long haul for BAV.
I'm running fsx acceleration, in windows 8.1 pro, using a Mad Catz FLY5 flightstick.