XNA 4.0 Game

Hey Im making a "space shooter game" in XNA 4.0 and im haveing some trouble getting good movement. I want easy movement (press right to move right, left to move left, upp for upp and down for down) but I want a acceleration towards that direction when i press the button and I want it to decelerate when I stop pressing the button. I tried but im at a dead end.

Why are all ``games'' made in XNA are ``abstract space shooters''?
Because the only people to ever want to use XNA don't know shit about programming and are thus unable to produce something even slightly complex or entertaining.