Mac won't boot up from External Hard Drive

[MacGeek767]

Hello, today I turned on my MacBook and held down the option key to boot into Vista. When the hard drive i could boot from appeared on the screen, I noticed my external hard drive wasn't on the list. My Mac recognizes the hard drive, but it doesn't show up as a bootable option.

If this helps, I backup my files using SuperDuper (which makes the hard drive bootable) and I don't think Vista recognizes the drive either (it's formated for Mac OS X)

 

[NewMacbookPlz]

The external drive may not be setup to be a bootable drive?

I think when you set it up, there's an option in Disk Utility you have to select to make it bootable. In order to boot an Intel Mac off an external drive, it must have a GUID partition.

If it's regular Apple Partition Table, any PPC mac can boot it, and any mac can read it. If it's GUID an Intel mac running 10.5 can boot it, and 10.4 can read it as well. If it's a Master Boot Record setup, it's PC-bootable/read-write enabled, and mac read/write enabled./