***UPDATE***
I thought that this is the appropriate place for this.
To begin the dark road to Dreamcast softmodding you really only need a very general knowledge of how the backup process is done.
I am going to bypass all the technical junk (like I almost always do) and say this:
There is 2 ways (that I know of) to play backed up games. First is a special iso boot loader you can find if you google. Second is a patched iso.
Now the first option is very simple. Pop in the boot loader, wait for the Sega logo, then you see a strange looking dog with antlers (no joke!), then you put in your backed up cdr game. You are good to go.
*** THE NAME OF THE BOOTLOADER IS "UTOPIA BOOT CD" ***
Second option is even easier, you just play the backed up game. These games are patched with the proper boot sector to allow the games to load from the console. I should point out that most popular games have been patched and work fine. PROPS go out to the group ECHOLEON who did most of the games I have.
If you are just looking to get some games working on your dreamcast box I suggest downloading the iso's. NOTE: Dreamcast are not dvd size. They are cdr size (700 megs or smaller).
If you need the bootloader and cant find it, msg me and I will see if I can dig it up

If you need instruction on how to burn or backup original isos I may make a tutorial when I have more time.
For now if you have the iso on your hard drive use an app like Alcohol 120%
Hope this helps
MIKEMAN