One thing I neglected to mention is that external HDDs are almost always formatted for use on Windows systems.

You can buy external HDDs which come packaged with the "for Mac" nomenclature, but all this means is that they are pre-formatted using Mac OS X's native filesystem format, and probably include Mac versions of the backup software (or whatever comes with them).

Annoyingly, I've seen that 'for Mac' versions are more expensive, and really, there's no reason for that condition to exist.

Disks are just magnetic platters, which can be formatted using whatever filesystem your OS supports. Formatting a disk is a simple exercise.

If you wish to use the HDD manufacturer's software, a version for your OS can be downloaded from the manufacturer's Web site.

My advice to Mac users is not to bother with 'for Mac' versions, particularly if they're more expensive than the Windows versions.

Disks are OS-agnostic. What matters is the formatting you apply, and the availability of software (if you need it) for your OS.

As per my previous post, I don't use any of that software; I just want a big, plain disk.