I am creating a 2D farming game using XNA - just today I have tried applying full screen to it, and I realized I failed badly with something. It cuts off a bit of the lower part [item hotbar and a piece of character status area]

I have just started learning C# and XNA, I just totally rewrote the engine and changing everything with rendering all over again is not an option - honestly I have no idea myself how does it all work anymore [I'm using some crazy camera class thing with an array of rectangles for displaying tiles / moving them around when the player moves etc] :-P

In the previous version of the engine I used the default XNA window size and the full screen worked just fine, this time I changed it to something more ... comfortable, and it does not work anymore. Changing the preferred buffer width does nothing at all in full screen, it's still cut off, and still the same height. I have no idea what matrices or viewports are, and everything I seem to find on google refers to them and some crazy complicated stuff

The screen size I am using is 800 x 640

My screen is very long sideways [whatever the name for such screens was :|]

Is there a way to fix that without rewritting everything?