Thanks for your prompt support elindalyne !
I have a feeling that, even though I am manually login in with my main account (not the Gmail one that I've mentioned before), which is the one that should have full control, I go to this folder > right click on it > properties > security .. and the first thing is that I don't see the "authenticated users" option, I believe I'm NOT logged in as an full controller (Administrator). The reason I say that is because following this process, I don't have permission to change anything. I'm not even allowed to add a new account, as you have given as an option too.
10-14-2015 11:24 AM