question on install discs

I just installed photoshop elements 10.  There are a set of 3 discs in the disc holder inside the photoshop packaged labeled disc1 disc 2 and disc 3.  I put tindisc #1 and it churned for a couple of minutes and then came back with a dialogu box that said successfully installed and to click done.  Does anyone know what discs 2 and 3 are for ?  Thanks