As the title says I cannot select free flight in the FSX menu. I can select any other option except for free flight and multiplayer. However, although I can select missions, I cannot start them either. Any help or advice would be appreciated. I am currently attempting a full reinstall to see if that rectifies my issue. 

First thing to try is renaming your fsx.cfg file in your users\xxxxx\appdata\roaming\microsoft\fsx folder (xxxxx= your username) or where ever your OS sores your Appdata folder. Then let FSX rebuild a new one for you.. If that don't work you may have to reinstall FSX.