On start-up I get a white screen and the...

Your Computer can't find a system to boot (?), so you need to boot from your CD. Once booted from the CD, run Disk Utilities to see what's wrong. If it sees the drive, then repair it, fix permissions, if it does not see the drive, then it might have gone south. If it can't be repaired, then you will need "DiskWarrior", to see if it can fix it. If you have a current Backup