iTunes Sign-in

Hey i updated iTunes to the newest version 7 and now everytime i go into iTunes the sign-in screen pops up for me to type in my username and password then click check. How do i keep it from doing this. Oh and in my account info it says "two machines are authorized to play music purchased with this account". That 2nd machine is our other computer. How do i get it off our other computer and make it stop trying to sign me in every time i go into iTunes?