I got a USB HDrive from my parts box, initialized it for Mac OS X, did a brand-new, full time Machine backup to the HDrive and thought I was ready to upgrade from Leopard to Snow Leopard. Not so fast, my Mac says. When I try to install to the HDrive in the Mac, I get the message:
Mac OS X cannot be installed on "EDP24_HD". This disk is used for Time Machine backups.
Huh? This is the system disk we're talking about -- the one internal to the Mac itself. That's never supposed to be an option for a Time Machine backup. Maybe it's the fault of the cloning process... or something. Some research is definitely needed here.