How to Troubleshoot Microsoft Flight Simulator X Activation Errors

1. Run 'Microsoft Flight Simulator X' in compatibility mode. If you are on a PC running Windows Vista or Windows 7, right-click the desktop icon for the game and select 'Properties.' Select the 'Compatibility' tab and check the box next to 'Run this program in the compatibility mode for:.' Select 'Windows XP' from the drop-down menu and click 'OK.' Run the game again.
2. Repair your installation. First, download the 'Software Licensing System Reset Tool' (see Resources for link). Run it by double-clicking the EXE file that you have downloaded. Once this is complete, place your 'Microsoft Flight Simulator X' disc into your optical drive and click 'Repair.' Follow the basic on-screen instructions to repair your game install.
3. Install the game on a new user account. First uninstall the game by placing the disc in the CD or DVD drive on your PC and clicking 'Uninstall' from the list of options. Create a new user account by opening your Start menu and typing 'account' into the search box. Hit the 'Enter' key to go to the 'Manage User Accounts' screen. Click 'Add' to create a new account. Log in to the new account and reinstall the game.