SGD Howto Boot
Either you have a Super Grub Disk Cdrom, Floppy or USB what you have to do is insert Cdrom, Floppy or plug the USB just before starting your computer. If SGD appears at boot you do not have to do anything.
If SGD does not appear you should tweak your BIOS settings so that the SGD where device is installed boots in the first place.
Here there are two links which might help you: