Horrible Groan when computer turns on

[Bow Wow Brother]

I have a 'Dinosaur' [G3 upgraded to G4] when I 'turn it on' [not boot up] after its been off for a while [overnight] It makes a horrible groaning noise that eventually after [a few minutes - sometimes up to five] stops > but not completely [only in intensity > I can still hear it..... thou it's much quieter but still annoying > After awhile...... like if you live next to a constant sound [BART , Freeway, Airport] I can 'Tune it Out'

 

[Greenman]

If it's the hard drive, it is likely about to fail and if(when) it does you will lose all your data. If you are sure it is the hard drive, don't even turn your computer on except to make a backup. My advice: make a full backup and then a data-only backup. Then buy a new hard drive, don't wait for the old one to die.

Another possibility: your CD or DVD drive has become "loose" (discs no longer seat firmly). These can make quite a bit of noise when a disc is in them.