How can I backup my Sega Dreamcast games?

You can't - at least not yet anyway. You see, Dreamcast games use a completely different file structure to CD-Rs, which allows them to hold up to 1gb of gaming goodness on a single CD. These CDs are known as GD-Roms (the GD stands for Gigabyte Disc). The upshot of this is that you can't just make a 1:1 copy using your ordinary CD writing software and CD writer. At present, ripping a Dreamcast game is a very complicated procedure, the exact details of which are still kept closely under wraps. For this reason, you can't just pop a game disk into your CD writer and make yourself a duplicate from it.