Thanks for ´ur reply "eagle of fire", but I did it before post my problem. I mean, also I put in dosbox.cfg _Fullscreen:true_ when I execute dosbox.exe for did it in full screen but happens too.. I have to say, the first time I play Flashback did it in full screen but after that (I don´t remember change anything in dosbox config) I´m unable to play it again.. and I´m really, really lost!!!
Thanks at all