Thanx to everyone for the aswers.
I'm using a legal copy of Windows 10 (I'm actusally mostly an OS X and Linux user, where I didn't have any problems, but wanted to try Free Pascal on Windows, too), and had tried with both 32 bit and 64 bit versions of FPC.
I'm using avast antivirus and, as suggested, if I disable it before running the programs compiled with FPC they work (if the antivirus is enables, they hang immediately, even a simple hello world program).
Is there a way for not having to disable the antivirus before launching the executables?