iMac PowerMac G4 circa 2004 running OS 10.5.8. I was upgrading software when power went off, battery backup died and computer turned off. Since then when I try to boot it does not chirp, but goes to apple logo, then to the black "You Must Restart" multi language screen. it will boot in safe mode and run some of my programs, and will boot from backup external drive. When I try to run DiskWarrior or Teck tool Pro I get the message, "can't unmount Macintosh HD, close running programs and try again". I can't find any programs running from the internal drive. I have run what I can from DiskWarrior such as repair preferences, but still same result. Any help appreciated.