Re: file ownership
No operating system will "take ownership" of files on another disk. It doesn't work that way. The files on any other disks will stay on the other disks, untouched, until you modify them. When you modify files, they stay in the same format they were before and can still be used on any operating system.
If you put files onto the other two hard disks they will still be usable on other operating systems of course.
Can you describe the symptoms of this "claim ownership" thing that you said happened on Ubuntu 11.04/11.10?
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.