The image on my tv is not centered when I startup X, however when i run nvtv and selects 800x600 small and press apply, everyting works out fine. Is there a way I could have that done automatically at boot time???
I'm a newbie! Please tell wich files to edit in and so on..

yes it can be done from command line an put in your x init scripts. And I'm not trying to be mean, but I don't use it anymore, and can't for the life of me remember what file it goes in or the command line syntax, but google found it for me relatively simple back when I did it.