Help installing the Sims 2!? Wont read disk 2.?

Im trying to install the Sims 2 and it read disk 1 and it said to put disk 2 in. I did and then it poped up to again put disk 2 in. I got it out and cleaned it with my pj leg and it still says to put disk 2 in! What is wrong with it? What can i do to fix it and to install it?