Just zero it out from Disk Utility>Security Options. You'll need to be booted from a clone or the install DVD to do this. One pass zero will be more than sufficient. But make sure you have a completely reliable clone or TM on an external drive before doing this. You would reverse clone back to the internal when you get the G5 back, or restore from TM.
Or you can move all your sensitive data into an encrypted disk image first, then delete it from its original location.
And how can I access Disk Utility if the iMac has black screen? (no display at all). Also, the video-out connector is quite uncommon, even at the Apple Store on my location didn't have an idea about it, and they didn't have any adaptor either (btw, if it's the GPU what's broken, plugging an external monitor wouldn't work either).
Btw, on this iMac I have two accounts, one for the superuser, and another for the normal user, and both of them are password-protected (but not encripted). Do you think this would suffice for the disk being reasonably unreadable at the Apple repair team, or can they log into the machine without any of these two passwords?
I think you will just have to relax and assume they won't be interested in scouring your files. It's not like they don't have other things to do. Very small chance they will even bother to see your work. It's precious to you, but not to them.
Not saying this is at all likely, but if anything they'd probably be much more interested in lifting your iTunes music, if you have any.
After contacting two official Apple service sites, they told me they no longer have parts for the 20'' iMac G5, so it seems I won't be able to repair it.
It makes me a bit sad because I recently reinstalled all my stuff on its hard disk (with Tiger), making it very well tuned for my work. I didn't lose anything because I keep backups of everything, but it's sad to lose the hours I spent tuning that hard disk installation.
Do you know if I can still get this iMac logic board somewhere?
Or alternatively, is there some way I could reuse this hard disk with another machine? What machine? (keep in mind it's Tiger, and my iMac has a G5 CPU)
Thanks a lot in advance!