Time Machine External Backup Disk Icon I bought a new external hard drive to use with Time Machine: The Western Digital "My Passport for Mac" 1TB USB 3.0 Hard Disk Drive. This is the second hard drive Time Machine uses, the first one being my previous external disk. Therefore upon mounting my new disk, I did not receive the dialog box asking if I wanted Time Machine to make backups to this external disk (I believe you only get that dialog box if you haven't set up Time Machine before).

The icon for this new drive, both on the desktop and in the finder windows and sidebar, is the generic orange USB device. How do I get it to look like the hard drives seen in Time Machine preferences? I'm talking about the greenish-blue hard drive icon with the counter-clockwise arrow on it.

I thought when you set up a disk with Time Machine, it automatically changes its icon. Am I wrong about that?

[My first backup disk didn't have a traditional icon&mdash;it was a Toshiba disk and it came with its own red-and-black design, so I thought that overrode the Time Machine icon.]

System specs:


MacBookPro6,2 (mid-2010 version)
2.4 GHz Intel Core i5 processor
OS X 10.8.2 Mountain Lion
When you buy an new hard disk, normally it's formatted with a FAT32 file system that is not compatible with TimeMachine.

In order to use the HD with TimeMachine, the file system myst be HFS+ Journaled. Use Disk Utility to format the hard disk with HFS+ file system and go to TimeMachine preferences, you should now be able to use it.