OK - I have a G4 QuickSilver 867Mhz / SuperDrive, with 2 HDs: one HD running Mac OS 9.2.2 - the other running Mac OS 10.2.6. Here's the problem: When swapping between one HD to another - let's say from the OS 9.2.2 HD to the OS X HD, it will not boot up (and visa-versa). Either way - what I get is a blank gray screen (if switching to the HD running OS X - a blank grey screen which eventually displays the grey Apple with a circle around it and a cross through it - or if switching from the OS X HD back to the OS 9.2.2 HD - a blank grey screen which eventually displays the old nasty blinking question mark) - and I know that this is about to happen because even with the speakers "off" - the tower emits an odd double-beeping sound every 10 seconds - over and over until it displays one or the other OS's non-bootable symbol. I have double checked the jumpers on both HDs - and the Master / Slave settings are correct. I have performed several Clean Installs on both HDs - occassionally swapping round which one OS 9 and OS X are on - but this has not resolved the problem. The only way to make sure it does not happen when restarting into either HD, is to slect the Startup Disk, do a complete shut-down, wait 2 minutes, and restart the G4 with the mouse button held down in order to cause the Super Drive to eject on startup. If I put my ear to it - without Mouse down on start- up, I can't hear either HD spin-up. Only by causing the Super Drive to eject can I hear either HD begin to spin up. It's like both HDs depend on the G4s Super Drive to eject in order to get the signal to begin spin up. I have had my apartment tested for electrical faults and have had the G4 taken back to Apple Servicing, yet noone can detect the problem. One HD is an IC35L040AVER07-0 (40 GB) and the other is a Maxtor 5T060H6 (60 GB) - and yes - I know Maxtor is an unfavourable brand - though I have a sneaking suspicion that it wouldn't matter what HD I had in - as it appears to be .... an allusive electrical problem? Any ideas? Or any other ideas since Apple Service Centres are also without conclusion? cheers clockwork