My wife turned on her iMac G5 (rev a) 1.8 20" this morning and it couldn't find the filesystem (little folder switching between ? and the mac face). I did a quick hardware test and came up with a "disk system" error: 2STF/2/3:S-ATA Bus 0 - Master. Anyone shed light on what that means? I can hear the disk spin up and initially read it (nothing sounds mechanically wrong). It is plugged into an APC Smart-UPS (so power surge shouldn't be an issue). If I boot to the install disk I cannot run a disk check because it doesn't see a partition on it. Startup disk selecter is no help because it can't find the OS partition. When I run the hardware test I get the error above. I suspect the disk is OK and the data intact, but there might be a controller issue?? I don't have any other disk utilities to try and check it. I think this machine is still running 10.4.0 (obviously I can't check). Thanks much for any help, I thought I'd try here before braving an Apple Support call.