FSX won't start up again (Vista)

i installed fsx on my computer which runs on vista. unfortunatelly fsx won't start up again. every time when i insert dvd fsx, fsx can only be reinstalled or removed. where can i find fsx exe file for normal start up of fsx software? i tried to solve the activation problem by installing service packs 1 and 2 but it doesn't work neither.

thanks