Photoshop question for a n00b
 

I have sort of a before and after project im tinkering around with in photoshop. I started with the same pic and made a copy of it to actually work on. I'm trying to find an easy way to select the same portion of the photo in both pics as sort of a before and after comparison.

Using CS2, I'm sure the answer is right in front of me but like the subject line says..... i'm a photoshop noob.

Take the old picture and paste it as a new layer on top of the new picture and then you can select the portion of the old picture you want and then click onto the new picture layer and the selection will switch between layers.