Not quite sure what you mean by "recorded by a Vista laptop which I cannot transfer to my XP desktop." Most photos taken with a digital camera are in jpeg format (suffix.jpg) and can be viewed in Vista and XP. You can "drag" the pictures from your CD drive on your XP machine that you want (typically My Documents/My Pictures) or to your desktop if you want, or to any other folder. You should also be able to view them on your CD-R by right clicking the CD drive and use Open or Preview.
If you really want to know the suffix that your photos have been recorded with open just about any window, click on Tools, Folder Options, View and untick the box that says "Hide extensions for known file types." When you refresh the folder you will see the file extensions and that will tell you if your pictures are jpegs or some other format.