My G5 mac wont burnt dvds anymore. It gets an error message. I googled the error message and read up on alot of tips to fix situation. So I decided to install OS system again and keep archive files. It must be my dvd harddrive. Because when I go to install, half way through it wont install. When my mac boots up again, its asking me questions when I FIRST registered it. I have a new system and I want my old system back. I looked through my harddrive and it says previous system. THATS the system I want loaded back up. How do I do that??