You're not kidding when you say "broken engine"... sounds like a spun bearing in a V6 engine.
Diagnose it like a broken engine then. Open the case wide open, start the machine up and listen for the horrible noise up close. It'll be either your hard disk or one of the fans. Disconnect the suspected component and see if the noise goes away. Once it does, you've found the problem.
If it does turn out to be the hard disk, you may wish to take the cover off and fire it up with the cover off just to see what's caused that awful racket. Although for a sound like that it would have to be nothing short of a broken actuator arm.
Just from the fact alone that you said OS 9 crashed exactly prior to the noise, i'd say the hard disk has self imploded in a BIG way. The sound of it clunking and spinning down at the end of the audio clip sounds very metallic, like metal on metal. You wouldn't get this kind of sound with a plastic fan, that's for sure, but you would get the exact sound from a disk platter.
Best of luck.