How can i fix my screen?

While i am playing in my bingo room ((or any place )) if i have it on auto after about 3 mins if my mouse is not moved in that time my screen will change and go black and the windows xp logo will come up... is there some thing i can do so that my screen doesnt change if im on auto and mouse isnt moved for awhile... i just changed puters and my other puter didnt do this... kinda irritating if u r doing some thing and screen keeps changing thanks for any help points