Reinstalling AIM

I have had aol instant messanging for a while now…maybe a year…and when i went to sign on today..and i clicked on the box and it won’t come up…it tryed cloning it and that wouldn’t work then i tryed going into the program and starting it that way but nothing worked…i did save my buddylist and i wanted to re-download aim but the problem is…when i went to go download it..i had to make a new screen name and i wanted my original one..so how could i re-download aim and keep my original screen name..thanks alot