Thanks a lot for your kind support!!!
I’ve tried the methods Steve Brown suggested me but it still didn’t work. After reading Dave’s explanation, I understood that my computer is not powerful enough to run Ae. Unfortunately I can’t afford to upgrade to 8GB RAM at the moment, I am planning to upgrade to 8GB Ram and SSD in the future.
I think I will stick to the Premiere Pro CS5 for the moment, but I really miss the features of Ae 🙁
Again, thanks so much!!!