Re: downloading and using .tar
Ubuntu 5.04 is ancient. Don't use it. I doubt Flash Player 10 would work on it, and I'd be surprised if Flash Player 9 would work. Any version of Flash Player that's older would be next-to-useless.
Ubuntu has never had a root account; instead you use 'sudo' to temporarily gain root permissions.
In later versions of Ubuntu, you simply install the 'flashplugin-nonfree' package using your package manager, so don't bother with the tar.gz. Just download Ubuntu 10.04 and it will be able to retrieve this package for you.
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.