Put your FSX disc 1 in the CD/DVD drive, and do a repair of the FSX installation. If you have Acceleration, do the same for that, put the Disc in the drive and do a repair. If you don't have Acceleration, then reinstall SP1 and SP2. FSX Gold is the same as having FSX Deluxe & Acceleration.

Be aware that if you have Acceleration, when you install it,  will install SP1 first, then install Acceleration with its own version of SP2.

This should fix FSX.

Mark