Yay!!

It finally works, that's what I did:

1) Uninstalled completely nHancer and Nvidia drivers (to uninstal nvidia drivers i used "driver sweeper 2.1.0" tool)

2) Rebooted

3) Installed nVidia lastest drivers.

4) Rebooted

5) Installed nHancer and configured it

6) run FSX

7) crossed my fingers 



I hope this can be helpful for some1 else, thanks a lot for your replies, expecially the last one of olderndirt that made me try and retry with a bit more of hope!!