Let's consider you are looking for a file named letter182.abw somewhere in your CD stack.
First launch GTKtalog and open your previously saved catalog File->Recent Files->You file or File->Open if you cannot find that catalog in the recent files list. GTKtalog displays an activity bar in the lower right conner to indicate that it is loading the catalog file.
Click on the "Find File" button of the toolbar. Type the file you search (here letter182.abw). If you don't know the exact name of the file you are searching for please see Chapter 8.
Click on "Start Search". In the results list, you can find the location of this file inside the catalog along with some additional information. In order to get this file back on your hard drive you only need to insert the CD and retrieve the file with your favorite file manager (Gnome Midnight Commander, Nautilus, Shell Command ...).