I was messin with my computer and changed the dpi and now I cant change it cuz everything is too big! HELP!!!!

I was tryin to change my screen size so it would fit my tv size. now all the windows and fonts are huge and I cant even change it back cuz the link I need to click on is off screen and my mouse wont allow me to move the window any higher to even try to click it. I cant system restore due to the same problem. everyhing i can possibly think of is off limits due to the fact the on is off screen. To be honest I didnt even think I would be able to post this cuz everything is so big. someone help me with this problem please! All I wanted was for my laptop to be connected to my tv and now that I have the cord I needed I cant even see anything on the screen. If someone could just give me an answer to this it would be a life saver. I have tryed so many options and nothing has worked. PLEASE HELP!