After that, I registered in Addon Manager and since then I am having consistent crsh to desktop in FSX. It does not come up at all.
If I follow this report to the letter, it looks like you didn't had any crashes *until* you registered your Serial ? Sorry, but this is not possible, really. If the scenery had a problem like that, it would have been apparent regardless of the registration. There's no difference whatsoever between the full version and the Trial version, they are bit-by-bit identical, and you don't download anything else after the registration.
And, please be more specific about this crash to desktop: does it happen when loading FSX, when starting a flight, or after some time ? Do you see any error messages ? If yes, which ones ?
On the first try I was asked to activate some software and keep it trusted for other uses of FSX.
That's exactly what is supposed to be happening.
