Hey, I also had this happen to me on my 9500. Turned out it was a bad bearing in the fan. Quite loud indeed.Replaced the fan and the noise went away. Just a thing to look into before you by a new drive. But back up!!! You never know. CJ PowerMac 9500 Upgraded to G4/450Mhz 768 MB RAM XPostFacto- MacOS 10.2.6 Radeon 7000 PCI ATTO SCSI Card SCSI HD 36GB Secondary HD 2GB