Go here: www.limewire.com

Click on "2.4" on the front page, and it bring you to the download page. Download for your platform (windows, mac, linux, what have you).

After its downloaded, just install like the first time. It should automatically bring back up any music & such you had in the library window (unless you changed the directory to something wacky in your first install.)

Also, If you dont have Java 1.4, I suggest you get it. http://java.sun.com/