CS9 Layers Disappear on v7.0 and shows up at flattened/locked "Background"

I have been using Photoshop CS2 to make psds and they're multilayered files when saved as a PSD, however, opening the file up in Photoshop v7 at school's yearbook room simply makes all the layers seem flattened, the only layer showing up says "Background" with a lock beside it. How do I make sure version 7 can see these layers? In CS2, when I save a file, I always use "Maximize compatibility" however, I always seem to get a composite single background layer (similar to what you would see when you open up a JPG) in PS7.

How do I fix it so I can see all layers in PS7?
Thanks!

Are you using 16 bit/channel images? If so, Photoshop 7 doesn't support them, and only the composite (flattened) image can be read by Photoshop 7.

If you want all the layers in PS 7, you'll have to convert down to 8 bits/channel..

Thank you so much!
That was my problem!