Partition or not to partition....that is the question

I'm a newbie with a mac mini. My question is:

My Mac Mini doesn't have a optical drive. I made a bootable partition (GUID, 50GB) on an external hard drive so I can install Snow Leopard. Does the whole external have to be bootable in order for it to be recognized?

No.
A partition can be bootable, and a single disk can have multiple partitions.
OS X will recognize partitions at the OS level , bootable or not.
OS X ( Disk Utility ) will recognize disks at the hardware level, partitioned or not.

Cheers ... McBie

The reason I ask is because, when I press the Alt key, (Microsoft Keyboard). a dropdown list shows no bootable device. That tells me that I have no internal hard drive installed. Wouldn't the external hard drive still show in the list?

In what application are you pressing the ALT key ....
Are you running the OS X disk utility ? Is you external disk visible in Disk Utility ?

Cheers ... McBie

There isn't any OS that I can see. When I turn on the mini, I press the Alt key and that shows what bootable devices are available. Mine doesn't show anything, not even the external with the bootable partition.