I'm not quite sure if I myself can fix this but I've been using my computer for about a year now just keeping the installation disk in the drive.. If I remove it, it will not boot when powered on. It hasn't always done this. When powered on without the disk it says something like "please insert cd or dvd" Thanks!
I did exactly what you said. It did not work though unfortunately. I had the system disk out of the computer when it booted and it says "Verifying Dmi Pool Data..."
"DISK BOOT FAILURE; INSERT SYSTEM DISK AND PRESS ENTER..."