Mac G-5 to Digital Display


I have a 22inch Apple Cinema Display connected to a Power Mac G5 with dual 2.0 processors, running Tiger 10.4. I am trying to send the image on my monitor to a digital projector in the front of the room along with viewing the work on my Cinema Display(at the same time). I am having a real problem doing this. In the back of the G-5 there are two DVI Display ports and I have tried using both with the same results. I do not get an image on the projector and monitor at the same time or if I do get an image on the projector I only see a small portion of the Monitor screen not the entire screen. On page 23 of the Power Mac User Guide it says to go to System Preferences, click on Displays, and Choose Mirroring. I cannot find anything on the Display page about Mirroring. Is that because I am using a Cinema Display. I need to project the work for my class to see what I am doing and it would be great to see the info on my own screen at the same time. How can I fix the problem.

Thank You