Just to be clear, the "System Repair" DVD is not used to do a reinstallation in the future - it's used to restore a "system image" backup.
The idea is that you use "Backup and Restore" to make a "system image" backup to another disk (typically an external hard drive). You also use the same program to burn a "System Repair" DVD. You only have to burn the DVD once, but you can make "system image" backups as often as you like.
In the event that the hard drive holding your OS dies, you can replace the hard drive with a brand new one, then you boot from the "System Repair" DVD and then use it to restore the OS from the "system image" backup you made.
jimmysmitty's answer to your original question is correct - you create the DVD by using the Backup and Restore program. You can also get to that program using "Start --> All Programs --> Maintenance --> Backup and Restore".