Backing up on macs

[Rave]

Probably, but I didn't wanna chance it.

I know they are because I use two of them for cloned backups

[bulo]

None of ours external drives support the installation of a operating system on it, like Windows XP or Vista or MAC leopard etc, etc.

I've install Leopard and then restore with time machine on an external WD about a week ago after my HD crashed, and I'm using it right now.
And it works well.
Strange.