Scrolling Pics on a USB device

Hi

I am a completely new user to the apple i mac and I can't seem to scroll through pictures on a USB memory stick. It says that the pics are locked and I have to select individual pics to view.

I can scroll through the thumbnails just like the artwork on a i pod but not through full size photos..

Any suggestions please ?

Try pressing the space bar (for Quicklook) after selecting one and then using the arrow keys to change pics.

Thank You so much, what a star. Just did this and bingo... Excellent. Very happy now