One of the questions we see time and again is whether or not Mozy can backup USB (external) drives. Well, since we have a Mozy account, and we have an external drive, we thought we’d give it a shot.
Update: Be sure to read this post in the Mozy Support section, Does MozyHome support external drives?
First, open “My Computer” (or, on Vista, simply “Computer”).

Next, find your external drive, right-click, and choose “Add to MozyHome Backups”

Well, that was easy. How can you test if it worked? Simple: open your drive and look for Mozy’s icon overlays. If you see a red exclamation point over the icons, it’s in the backup set, but not yet backed up. If you don’t see anything, hit F5 to refresh the view.

One thing we’ve heard, however, is that an external drive that isn’t present when the backup starts will be dropped from the backup set. So we tested this theory.
We unplugged the external drive, then manually started the backup process. Once the backup was done, I plugged the USB drive back in, and checked for the icon overlays again. To my surprise, they were there! Hrm… maybe just a display bug. So I checked my MozyHome configuration, and the “G” drive was listed, and checked to be backed up!
Since my “G” drive is my local backup (using Acronis), I unchecked it, as a backup of my backup is a bit much, especially when it’s 140GB in size!