Can you be a bit more specific? When you post a questions on a forum there a rules.
Provide your system specs and a description of what you want to achieve.
If you want to boot into an already installed Linux distribution you need to reinstall the boot loader; Grub on your drive. He will detect the OS on your system and list them for you to start at boot.
Look here for a precise guide with a Ubuntu Live-CD (Also debian based):
http://ubuntuforums.org/showthread.php?t=224351
Without more detail I cannot help you more.
