Hello, WD makes great drives, but not great enclosures...
The WD My Books have had far less than glowing reviews for Macs...
http://discussions.apple.com/thread.jspa?threadID=1543028
http://discussions.apple.com/thread.jspa?threadID=2191614&tstart=0
http://x704.net/bbs/viewtopic.php?f=12&t=3219&p=42023&hilit=western+digital#p420 23
http://x704.net/bbs/viewtopic.php?f=6&t=2939&p=34120&hilit=western+digital#p3412 0
The following external hard drives are bootable on Intel-based Macintosh computers systems through USB:
• My Book Essential Edition
• My Book Essential Edition 2.0
• My Book Home Edition
• My Book Mirror Edition
• My Book Office Edition
• My Book Premium Edition
• My Book Premium Edition II
• My Book Premium ES Edition
• My Book Pro Edition
• My Book Pro Edition II
• My Book Studio Edition
• My Book Studio Edition II
• My Passport Studio
The following external hard drives are bootable on Intel-based Macintosh computers systems through FireWire (1394a/b):
• My Book Home Edition
• My Book Mirror Edition
• My Book Office Edition
• My Book Premium Edition
• My Book Premium Edition II
• My Book Pro Edition
• My Book Pro Edition II
• My Book Studio Edition
• My Book Studio Edition II
• My Passport Studio
The following external hard drives are bootable on Power PC based Macintosh computers systems through FireWire (1394a/b):
• WD My Book Premium Edition
• WD My Book Pro Edition
The following external hard drives are not bootable on Power PC based Macintosh computers systems through USB/FireWire 1394(a/b):
• My Book Essential Edition
• My Book Essential Edition 2.0
• My Book Home Edition
• My Book Mirror Edition
• My Book Office Edition
• My Book Premium Edition II
• My Book Pro Edition II
• My Book Studio Edition
• My Book Studio Edition II
• My Passport Studio
• My Passport Elite
• My Passport Essential
• WD Passport
• WD Passport (Silver)
That being said, Option Boot won't show until you Format it HFS+ & Install OSX on it, or clone the Internal.
How to format your disks...
http://www.kenstone.net/fcp_homepage/partitioning_tiger.html
Thanks to Pondini, Formatting, Partitioning, Verifying, and Repairing Disks...
http://Pondini.org/OSX/DU.html
As far as recommendations for a drive, the Quad Interface ones here...
http://eshop.macsales.com/shop/firewire/1394/USB/EliteAL/eSATA_FW800_FW400_USB